单选题It must comply strictly Uin/U safety standards to be accepted by the public, and at the same time it must demonstrate that no health or environmental damage occurs.

单选题As the Olympic flame was ______ and the flags lowered, the closing ceremony concluded with a firework display.

单选题She told me that she has already gone to the United States four times before she attended that conference.

单选题Alaskans love reading books about

单选题About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along free on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen. The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids.

单选题Hydroponics ______ the cultivation of plants without soil.

单选题All workers, regardless of their sex and education, are required to ______ at the age of 60.

单选题The eastern bluebird is considered the most attractive bird native of North America by many bird-watchers.

单选题I will go home for the vacation as soon as I have finished my exams.

单选题The girl made a light of her disappointment at being too sick to go to the dance.

单选题The fun of playing the game was a greater incentive than the prize.

单选题This passage, on the whole, is developed by ______

单选题The doctor said that the patient had______at once.

单选题It was a bold idea to build a power station in the deep valley, but it ______ as well as we had expected.

单选题She's cute, no question. Symmetrical features, flawless skin, looks to be 22 years old-entering any meat-market bar, a woman lucky enough to have this face would turn enough heads to stir a breeze. But when Victor Johnston points and clicks, the face on his computer screen changes into a state of superheated, crystallized beauty. "You can see it. It's just so extraordinary," says Johnston, a professor of biopsychology at New Mexico State University who sounds a little in love with his creation. The transformation from pretty woman to knee-weakening babe is all the more amazing because the changes wrought by Johnston's software are, objectively speaking, quite subtle. He created the original face by digitally averaging 16 randomly selected female Caucasian faces. The changing pro-gram then exaggerated the ways in which female faces differ from male faces, creating, in human-beauty-science field, a "hyper-female". The eyes grew a bit larger, the nose narrowed slightly and the lips plumped. These are shifts of just a few millimeters, but experiments in this country and Scotland are suggesting that both males and females find "feminized" versions of averaged faces more beautiful. Johnston hatched this little movie as part of his ongoing study into why human beings find some people attractive and others homely. He may not have any rock-solid answers yet, but he is far from alone in attempting to apply scientific inquiry to so ambiguous a subject. Around the world, re-searchers are marching into territory formerly staked out by poets and painters to uncover the underpinnings of human attractiveness. The research results so far are surprising and humbling. Numerous studies indicate that human beauty may not be simply in the eye of the beholder or an arbitrary cultural artifact. It may be ancient and universal, wrought through ages of evolution that rewarded reproductive winners and killed off losers. If beauty is not truth, it may be health and fertility: Halle Berry's flawless skin may fascinate moviegoers because, at some deep level, it persuades us that she is parasite-free. Human attractiveness research is a relatively young and certainly contentious field-the allure of hyper—females, for example, is still hotly debated—but those on its front lines agree on one point: We won't conquer "looks—ism" until we understand its source. As psychologist Nancy Etcoff puts it: "The idea that beauty is unimportant or a cultural construct is the real beauty myth. We have to understand beauty, or we will always be enslaved by it. /

单选题You cannot say that the desire for material advantage is the basic motive in human behaviors; there are many exceptions for this.

单选题If a ring is stamped 24K, it has ______.

单选题The most striking technological success in the 20th century is probably the computer revolution. A. profitable B. productive C. prominent D. prompt

单选题The integration of independent states could best be brought about by first creating a central organization with authorities over technical economic tasks.

单选题A good modern newspaper is an extraordinary piece of article.