[简答题]According to scientists, many people believe that physical cleanliness is strongly linked to ______.

[单项选择]Scientists now believe that many, if not all, living things are born with some type of hidden clock. These clocks are sometimes set by the number of hours of light or darkness in a day, by the rhythm of the tides or by the seasons. One of the most remarkable of nature’s living clocks belongs to the fiddler crab, that familiar beach-dweller with the overgrown claw. Biologists have long known that the crab’s shell is darkest during the day, grows pale in late afternoon, then begins to darken again at daybreak. This daytime darkening is valuable for protection against enemies and sunlight, and for many years it was thought to be a simple response by the crab to the sun--just as if we were to get a tan during the day and lose it at night. But when an enterprising scientist placed a fiddler crab in darkness, he was amazed to find that the color of the crab’s shell kept ticking off the time with the same accuracy. Yet another startling fact was revealed: the crab’s shell re
A. the fiddler crab’s shell reached the darkest color at the same time in Cape Cod, Massachusetts and its neighboring island
B. the fiddler crab continued to change color in the dark
C. plants will not grow without sunlight
D. all of the above

[填空题]Scientists believe that the things people do that send ______ gases into the air are making our planet warmer.

[单项选择]

Scientists who believe cell phones are dangerous have been throwing out hypotheses to explain away the negative results. Maybe something about the (34) animals raised their rates of cancer or sperm problems, so (35) the exposed animals didn’t seem to be harmed. Maybe the studies should have used pulsed, (36) radiation rather than a continuous beam, the better to (37) the way we actually use mobile phones. Maybe it matters (38) the lab animals are zapped (39) in a device like a Ferris wheel or while (40) around in cages. On the other hand, if these details do (41) , maybe that in itself is significant.
Scientists who (42) claims that cell-phone radiation is causing an epidemic of brain cancer (43) that there isn’t any mechanism. (44) textbook biophysics, only radiation that has enough energy to ionize molecules—that is, knock off electrons—can (45)
A. demolish
B. dismiss
C. conversely
D. strongly