单选题Poverty is not ______ in most cities although, perhaps because of the crowded conditions in certain areas, it is more visible there.

单选题--"Did you review your lessons last night?"--"No, but if I ______, I would have done better on today's test."

单选题In this passage, the writer is clearly stating the intention which is to get the reader to ______.

单选题 Birds that are literally half asleep—with one brain hemisphere alert and the other sleeping—control which side of the brain remains awake, according to a new study of sleeping ducks. Earlier studies have documented half brain sleep in a wide range of birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere's eye stays open and alert. Birds also can sleep with both hemispheres resting at once. Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end-of-the-row sleepers. Sure enough, the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction. Also, birds dozing at the end of the line resorted to single hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating 16 birds through the positions in a four duck row, the researchers found outer birds half asleep during some 32 percent of dozing time versus about 12 percent for birds in internal spots. 'We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness simultaneously in different regions of the brain,' the researchers say. The results provide the best evidence for a long standing supposition that single hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lookout side could be widespread, he predicts. He's seen it in a pair of birds dozing side by side in the zoo and in a single pet bird sleeping by a mirror. The mirror side eye closed as if the reflection were a companion and the other eye stayed open. Useful as half sleeping might be, it's only been found in birds and such water mammals (哺乳动物) as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning. Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UCLA says he wonders if birds' half brain sleep 'is just the tip of the iceberg (冰山).' He speculates that more examples may turn up when we take a closer look at other species.

单选题Our visual perception depends on the reception of energy reflecting or radiating from ______ which we wish to perceive.

单选题Without water from the Nile River, Egypt ____ a farming country and become a desert.

单选题A girl contemplates ______ a sweater previously worn by her ex-boyfriend, but she finds the garment repulsive.

单选题Whenever he comes across a serious problem, he likes to ______ it, namely, to think it about carefully and for a long time.

单选题The fund is for ______ distress among the flood victims in the southern city. A. releasing B. detracting C. relieving D. devolving

单选题—I am not quite myself today. —______go and see a doctor?

单选题The media's ______ in the presidents private life switched the attention away from the real issues.

单选题Mrs. Smith saw ______ in the old lady' handbag.

单选题The firm will ______ the workers ______ their loss of job.

单选题The author's attitude toward the construction of skyscrapers seems to be that of

单选题Recycling wastes slows down the rate ________ which we use up the Earth’s finite resources.

单选题Let's go on a picnic this weekend, ____ ? 

单选题There is nothing more possible than a new hip or knee that can put the spring back in your step. Patients receiving joint implants （移植） often are able to resume many of the physical activities they lo

单选题After a three-hour heated discussion, all the members in the jury reached the conclusion that the man was______of murder.

单选题The bus was so crowded that he had a hard time______.

单选题One of the important properties of a scientific theory is its ability to ______ further research and further thinking about a particular topic.