John is so strongly built that he looks as if he ______ an elephant.

He blew out the candle and ______ his way to the door.

All the people in the stadium cheered up when they saw hundreds of colourful balloons ______ slowly into the sky.

The previous section has shown how quickly a rhyme passes from one school child to the next and ill

I never regretted ______ his offer

Once you get to know your mistakes

马头琴是我国（ ）的民族乐器。

The twins are so much ______ that it is difficult to tell one from the other.

Fat cannot change into muscle ______ muscle changes into fat.

When the lost of money is reported to him

Ever since John Wheeler coined the phrase "black hole", these complex astronomical phenomena have held a peculiar fascination for physicists and laymen alike. Physicists are interested because of the extreme conditions inside and at the edge of a black hole—a region where gravity is so strong that nothing was thought to be able to escape. These conditions test the intersection between the two theories that lie at the heart of modern physics: quantum mechanics and Einsteinian gravity (the latter known, rather confusingly, as the general theory of relativity). Both theories agree perfectly with those observations that have been made so far. But the two seem to be incompatible with each other, putting out of reach one grand, unified theory. Many physicists would like to overcome this obstacle. Laymen are probably more captivated by Dr Wheeler's nomenclature than by the details of the physics. But black holes are not really black. In the paper that catapulted him to fame in 1974, Stephen Hawking predicted that some black holes should emit radiation (although in a manner that is still not fully understood). And now, it seems that another famous coinage by Dr. Wheeler—"black holes have no hair"—is also false. What Dr. Wheerler meant by the hairlessness of black holes was that they could be characterized by just three numbers: mass, angular momentum (roughly speaking, how fast a hole spins) and electric charge. To describe a star, one would have, by contrast, to say what each of the zillions of atoms inside it was doing. Once Dr. Hawking discovered that a black hole radiates, however, the lack of hair led to a paradox. Drop something—an encyclopedia, say—into a black hole, and it would be destoryed and eventually re-emitted as Hawking radiation in a random way. The information in the encyclopedia would be lost. But quantum mechanics dictates, perhaps surprisingly, that information cannot be destroyed. If the encyclopedia were to fall into a star it would be possible (though admittedly very hard) to reconstruct it by reversing the paths of all the atoms of which it had been composed. Before Dr. Hawking's paper, that point was finessed because no one could prove that the information was not somehow preserved within the black hole. But the Hawking radiation, which is predicated by an ad hoc combination of relativity and quantum mechanics, trumps that finesse and leaves an apparent paradox. In a paper just published in em>Nuclear Physics B/em>, Samir Mathur and his colleagues at Ohio State University seem to have solved the paradox using string theory, which is the best available attempt to reconcile relativity and quantum mechanics. This theory, which postulates that everything in the universe is a consequence of tiny strings oscillating in ten dimensions, was thought to have observable consequences only at very small scales—as much smaller than atoms as atoms are smaller than the solar system. Dr. Mathur showed, however, that at high densities of matter, such as those within a black hole, the effects attributable to strings can grow to large sizes. According to Dr. Mathur, the interior of a black hole can be thought of as a ball of strings. This ball modulates the Hawking radiation in a way that reflects the arrangement of the strings inside the hole. So, in effect, it acts as a repository of the information carried by things that have fallen into the hole. Thus, as quantum mechanics requires, no information is destroyed. Besides resolving the information paradox, this theory has the added benefit—at least in the special cases that Dr. Mathur has been able to work out exactly—of getting rid of the "singularity" that had been thought to lie at the center of every black hole. A singularity is a mathematical anomaly where physical theories such as general relativity break down because quantities that should be finite diverge to infinity. It would therefore be quite a boon if Dr. Mathur is correct, and singularities do not actually exist. His result also has a bearing on wider cosmological issues. The early universe would have had a density similar to a black hole, and so the "string-ball" theory would have applied there, too. Though Dr. Mathur is cautious on the matter, his theory might supply an alternative explanation about why—when viewed on the grandest scale—the universe appears remarkably uniform. At the moment, this uniformity is put down to a phenomenon known as cosmic inflation, in which the universe is supposed to have expanded rapidly when it was very young. That expansion would have "locked in" the universe's initial uniform state by stopping local concentrations of matter from forming. Tying the early universe together with strings might provide an alternative explanation for cosmic uniformity. String theory is often criticized because it abstracts and thus hard to compare with reality. But although no one can yet see a black hole close up, and thus test Dr. Mathur's ideas for real, the fact that string theory seems able, in this case, to resolve long-standing inconsistencies between general relativity and quantum mechanics is a big point in its favour. From the passage we know that ______.

When Edison died

This year some twenty-three hundred teenagers from all over the world will spend about ten months in U. S. homes. They will attend U. S. schools, meet U. S. teenagers, and form lifelong impressions of the real America. At the same time, about thirteen hundred American teenagers will go abroad to learn new languages and gain a new understanding of world problems. On returning home they, like others who have participated in the exchange program, will pass along their fresh impressions to the youth groups in which they are active. What have the visiting students discovered? A German boy says, "We often think of America only in terms of skyscrapers, Cadillacs, and gangsters. Americans think of Germany only in terms of Hitler and concentration camps. You can't realize how wrong you are until you see for yourself." A Los Angeles girl says, "It's the leaders of the countries who are unable to get along. The people get along just free." Observe a two-way student exchange in action. Fred Herschbach, nineteen, spent last year in Germany at the home of George Pfafflin. In turn, Mr. Pfafflin's son Michael spent a year in the Herschbach home in Texas. Fred, lanky and lively, knew little German when he arrived, but after two months' study the language began to come to him. School was totally different from what he had expected—much more formal, much harder. Students rose respectfully when the teacher entered the room. They took fourteen subjects instead of the six that are usual in the United States. There were almost no outside activities. Family life, too, was different. The father's word was law, and all activities revolved around the closely knit family unit rather than the individual. Fred found the food—mostly starches—monotonous at first. Also, he missed having a car. "At home, you pick up some kids in a car and go out and have a good time. In Germany, you walk, but you soon get used to it." A warm-natured boy, Fred began to make friends as soon as he had mastered enough German to communicate. "I didn't feel as if I were with foreigners. I felt as I did at home with my own people." Eventually he was invited to stay at the homes of friends in many of Germany's major cities. "One's viewpoint is broadened," he says, "by living with people who have different habits and backgrounds. You come to appreciate their points of view and realize that it is possible for all people in the world to come closer together. I wouldn't trade this year for anything." Meanwhile, in Texas, Mike Pfafflin, a friendly German boy, was also forming independent opinions. "I suppose I should criticize the schools," he says. "It was far too easy by our standards. But I have to admit that I liked it enormously. In Germany we do nothing but study. I think that maybe your schools are better training for citizenship. There ought to be some middle ground between the two." He took part in many outside activities, including the dramatic group. Mike picked up a favorite adjective of American youth; southern fried chicken was "fabulous." When expressing a regional point of view, he used the phrase "we Texans." Summing up his year, he says with feeling, "America is a second home for me from now on. I will love it the rest of my life." This exciting exchange program was government sponsored at first; now it is in the hands of private agencies, including the American Field Service and the International Christian Youth Exchange. Screening committees make a careful check on exchange students and host homes. To qualify, students must be intelligent, adaptable, outgoing-potential leaders. Each student is matched, as closely as possible, with a young person in another country whose family has the same economic, cultural, and religious background. After their years abroad, all students gather to discuss what they observed. For visiting students to accept and approve of all they saw would be a defeat for the exchange program. They are supposed to observe, evaluate, and come to fair conclusions. Nearly all who visited the United States agreed that they had gained faith in American ideals and deep respect for the U. S brand of democracy. All had made friendships that they were sure would last a life-time. Almost all were struck by the freedom permitted American youth. Many were critical, though, of the indifference to study in American schools, and of Americans' lack of knowledge about other countries. The opinions of Americans abroad were just as vigorous. A U. S. girl in Vienna: "At home, all we talk about is dating, movies, and clothes. Here we talk about religion, philosophy, and political problems. I am going to miss that." A U. S boy in Sweden: "I learned to sit at home, read a good book, and gain some knowledge. If I told them this back home, they would think I was a square." An American girl in Stuttgart, however, was very critical of the German school. "Over here the teacher is king, and you are somewhere far below. Instead of being friend and counselor, as in America the teacher is regarded as a foe—and behaves like it too!" It costs a sponsoring group about a thousand dollars to give an exchange student a year in the United States. Transportation is the major expense, for bed, board, and pocket money are provided by volunteer families. There is also a small amount of federal support for the program. For some time now, attempts have been made to include students from iron curtain countries. But so far the Communists have not allowed their young people to take part in this program which could open their eyes to a different world. In Europe, however, about ten students apply for every place available, in Japan, the ratio is fifty to one. The student exchange program is helping these eager younger citizens of tomorrow learn a lot about the world today. Exchange students are generally placed in homes that are ______.

It is strange that such a thing ______ in your school.

There was a knock at the door

The sale usually takes place outside the house

She ______ more embarrassed.

Of particular interest to visitors ______ the large number of bookstores that sell books in different languages.

Outside people were cheering and awaiting the arrival of the New Year while inside Harry was lying severely ill in bed feeling thoroughly ______.

Ignore all the grumbling you will hear in the next few days about Standard Poor's. Yes, the ratings agency miscalled tens of billions of dollars of mortgage bonds leading up to the financial crisis. Yes, it's an organization fraught with conflicts of interest, where debt issuers game the system to get the highest ratings. And yes, even in coming to its conclusion about the U.S. credit worthiness it appears SP's team of crack analysts made a minor $2 trillion error in calculating how much debt the U. S. would accumulate in the next 10 years (they said $22 trillion, but best guesses are $20 trillion). Know this: The ratings agency's decision on Friday to downgrade the credit rating of the U. S. government to AA+ from AAA—stripping the U. S. of the highest rating for the first time in 70 years—was 100% correct. There are a lot of reasons the U.S. no longer deserves the SP's highest credit rating. Not all are political. U.S. growth is slowing. The current recovery has dragged on at an anemic pace for more than two years, and it's not clear when that will end. Economists had been looking for the U.S. GDP to grow 3% this year. It will be more like 2%. But the slower growth trend is likely to extend past the current recovery, no matter when we pull out of it. The recoveries from the past two recessions have been among the slowest on record, and suggests the underlying strength of the U.S. economy is weakening. But that's just the beginning of why the downgrade makes sense. There's more: The aging of the U.S. population is likely to significantly boost healthcare costs and increase inflation. And a multi-decade long increase in the wealth gap in the U. S. has led to a vast increase in the amount of debt most Americas have. It has lowered the standard of our healthcare and education systems, and also made the U.S. more vulnerable to future financial crisis. But, to be sure, a large part of the current downgrade is political. And those aren't going away anytime soon, either. The fracturing of our political system has led to the rise of political parties that are unwilling to compromise on our biggest challenges. It is clear that the rise of the Tea Party and the pledge of Republicans in general to never raise taxes, along with the Democrats unwillingness to cut Social Security, produced the downgrade. In its decision to downgrade the U.S. debt, the SP specifically cited the lack of tax increases and cuts to entitlement programs in the debt ceiling deal as the reason they were lowering the U. S.'s rating. Worse, SP said the U. S. is likely to face a further ratings downgrade if the government continues to extend the Bush tax cuts for the wealthiest Americas. So what does the downgrade mean? Despite the mistakes SP has made in the recent past, it's ratings still matter. As I pointed out earlier this week, on average countries with lower ratings have higher interest rates. So borrowing costs of not only the U.S. government but also American consumers is likely to go up, even if not significantly at first. What's more, Treasury bonds, long one of the most stable securities in the market, are likely to get more volatile. That being said, one should not view the current downgrade of the U.S. debt as a new economic event. It is the latest blow that the U.S. economy has taken from the huge ramp up in housing and other debt that lead to the financial crisis. Economists have long predicted that the credit crisis would cause the U. S. economy to grow at a slower pace for years to come. How exactly that slower growth would play out was not clear. Now we have one more piece of the puzzle—relatively higher interest rates that will make it harder for the government, Americans and corporations to borrow money and expand. And after all the borrowing we have done in the past few decades, it's an outcome we deserve. Which of the following is firmly believed by the author?