单选题You can stay here ( ) you keep quiet.

单选题Your handwriting is ______mine.

单选题It is a source of continuing frustration that sometimes, after huge amounts of resources have gone into securing successful ______, career criminals often seem to be free after little more than a third or half of their sentences. A. convictions B. decisions C. vanquisher D. agreements

单选题The gloves were really too small, and it was only by ______ them that I can get them on.

单选题With a rapidly changing and ever-increasing customer expectations, it is time to rethink customer service training.

单选题 Biologically, there is only one quality which distinguishes us from animals: the ability to laugh. In a universe which appears to be utterly deficient of humor, we enjoy this supreme luxury. And it is a luxury, for unlike any other bodily process, laughter does not seem to serve a biologically useful purpose. In a divided world, laughter is a unifying force. Human beings oppose each other on a great many issues. Nations may disagree about systems of government and human relations may be plagued by ideological clans and political camps, but we all share the ability to laugh. And laughter, in turn, depends on that most complex and subtle of all human qualities: a sense of humor. Certain comic stereotypes have a universal appeal. This can best be seen from the world-wide popularity of Charlie Chaplin's early films. As that great commentator on human affairs, Dr. Samuel Johnson, once remarked, 'Men have been wise in very different modes but they have always laughed in the same way.' A sense of humor may take various forms and laughter may be anything from refined tinkle (清脆的声响) to an earth quaking roar, but the effect is always the same. Humor helps us to maintain a correct sense of values. It is the one quality which political fanatics (狂热者) appear to lack. If we can see the funny side, we never make the mistake of taking ourselves too seriously. We are always reminded that tragedy is not really far removed from comedy, so we never get one-sided view of things.' This is one of the chief functions of satire (讽刺) and irony. Human pain and suffering are so grim; we hover so often on the brink of war, political realities are usually enough to plunge us into total despair. In such circumstances, cartoons and satirical accounts of serious political events redress the balance. They take the wind out of arrogant politicians who have lost their sense of proportion. They enable us to see that many of our most profound actions are merely comic or absurd. We laugh when a great satirist like Swift writes about war in Gulliver's Travels. The Lilliputians and their neighbors attack each other because they can't agree which end to break an egg. We laugh because we are meant to laugh; but we are meant to weep too. The sense of humor must be singled out as man's most important quality because it is associated with laughter. And laughter, in turn, is associated with happiness. Courage, determination, initiative—these are qualities we share with other forms of life. But the sense of humor is uniquely human. If happiness is one of the great goals of life, then it is the sense of humor that provides the key.

单选题The policemen went into action ______ they heard the alarm. A. promptly B. presently C. quickly D. directly

单选题The use of heat pumps has' been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation. Heat pumps circulate a fluid refrigerant that cycles alternatively from its liquid phase to its vapor phase in a closed loop. The refrigerant, starting as a low-temperature, low-pressure vapor, enters compressor driven by an electric motor. The refrigerant leaves the compressor as a hot, dense vapor and flows through a heat exchanger called the condenser, which transfers heat from the refrigerant to a body or air. Now the refrigerant, as a high-pressure, cooled liquid, confronts a flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and partially vaporizes, becoming chilled. It then passes through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing the temperature of this second body of air. Of the two heat exchangers, one is located inside, and the other one outside the house, so each is in contact with a different body of air: room air and outside air, respectively. The flow direction of refrigerant through a heat pump is controlled by valves. When the refrigerant flow is reversed, the heat exchangers switch function. This flow-reversal capability allows heat pumps--either to heat or cool room air. Now, if under certain conditions a heat pump puts out more thermal energy than it consumes in electrical energy, has the law of energy conservation been challenged? No, not even remotely: the additional input of thermal energy into the circulating refrigerant via the evaporator accounts for the difference in the energy equation. Unfortunately, there is one real problem. The heating capacity of a heat pump decreases as the outdoor temperature falls. The drop in capacity is caused by the lessening amount of refrigerant mass moved through the compressor at one time. The heating capacity is proportional to this mass flow rate: the less the mass of refrigerant being compressed, the less the thermal load it can transfer through the heat-pump cycle. The volume flow rate of refrigerant vapor through the single-speed rotary compressor used in heat pumps is approximately constant., But cold refrigerant vapor entering a compressor is at lower pressure than warmer vapor. Therefore, the mass of cold refrigerant--and thus the thermal energy it carries--is less than if the refrigerant vapor were warmer before compression. Here, then, lies a genuine drawback of heat pumps: in extremely cold climates--where the most heat is needed--heat pumps are least able to supply en6ugh heat.

单选题It is more important that she should be free ______ she should live a luxurious life.

单选题Does everyone on earth have an equal right ______ an equal share of its resources? A. by B. at C. to D. over

单选题It was ______ for him to wear a T-shirt at the reception.

单选题By the time you get to Beijing tomorrow, I ______ for Shanghai.

单选题 Diabetes is one of the most prevalent and potentially dangerous diseases in the world.

单选题Have you ever heard of a flower whose seeds are carried and spread by elephants? The rafflesia, a rare blossom, is very unusual. Found in the rain forests of Sumatra, the rafflesia is the world's largest flower, measuring three feet in diameter! This giant flower is a parasite--it needs another plant to live on. It lacks the structures needed to survive alone. The rafflesia has no stem or leaves. It is all flower. It attaches itself to the roots of other plants and sucks their juices. The flower's favorite home is the root of the vine, which grows above ground. The rafflesia seems to burst right out of the forest floor. Its blossom weighs fifteen pounds! It has thick, spotted petals that give off a rotten smell. The center is about the size of a household bucket. After a rain, it may hold up to twelve pints of water! After the rafflesia dies, it becomes a pool of thick liquid in which its seeds float. Elephants wandering through the forest step into the mushy pool, and the seeds glue themselves to their feet. As the animals stomp through the forest, their sticky feet pick up twigs and leaves. The elephants try to rid themselves of the sticky mess, in the same way people try to get bubble gum off their shoes. The elephants rub their feet against the roots of the vine. In no time, seeds left on the vine grow into more monstrous flowers!

单选题However, at times this balance in nature is _____,resulting in a number of possibly unforeseen effects.

单选题In the development of a government agency, ______ .

单选题Man: Pam, I don't understand the problem. You've known for months this report was due today. Woman: I know... but I'm afraid I need another few days. The data was harder to interpret than I thought it would be. Question: What does the woman mean?

单选题According to BBC boxing reporter Mike Costello, just as there is worldwide ______ with boxing, so there is worldwide opposition.