Although no one is Certain why
migration occurs, there are several theories. One theory is based upon the
premise that prehistoric birds of the northen Hemisphere were forced south
during the Ice Age, when glaciers covered large parts of Europe, Asia, and North
America. As the glaciers melted, the birds came back to their homelands, spent
the summer, and then went south again as the ice advanced in winter In time, the
migration became a habit, and now, although the glaciers have disappeared, the
habit continues. Another theory proposes that the ancestral home
of all modern birds was the tropics. When the region became overpopulated, many
species were crowded north. During the summer, there was plenty of food, but
during the winter, scarcity forced them to return to the tropics.
A more recent theory, known as photoperiodism, A. there was not enough food there in the winter B. there were too many birds C. there were too many glaciers D. there was too much daylight
更多"Passage Five
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[单项选择] Passage Five
Although no one is Certain why
migration occurs, there are several theories. One theory is based upon the
premise that prehistoric birds of the northen Hemisphere were forced south
during the Ice Age, when glaciers covered large parts of Europe, Asia, and North
America. As the glaciers melted, the birds came back to their homelands, spent
the summer, and then went south again as the ice advanced in winter In time, the
migration became a habit, and now, although the glaciers have disappeared, the
habit continues. Another theory proposes that the ancestral home
of all modern birds was the tropics. When the region became overpopulated, many
species were crowded north. During the summer, there was plenty of food, but
during the winter, scarcity forced them to return to the tropics.
A more recent theory, known as photoperiodism, A. stopped migrating B. continued migrating C. began migrating again D. migrated south and stay there
[单项选择] Passage One
Although no one is certain why
migration occurs, there are several theories. One theory claims that prehistoric
birds of the Northern Hemisphere were forced south during the Ice Age. As the
glaciers melted, the birds came back to their homelands, spent the summer, and
then went south again as the ice advanced in winter. In time, the migration
became a habit in spite of the disappearance of glaciers.
Another theory proposes that the ancestral home of all modern birds was
the tropics. When the region became overpopulated, many species were crowded
north. During the summer, there was plenty of food, but during the winter,
scarcity forced them to return to the tropics. A more recent
theory suggests a relationship between increasing daylight and the stimulation
of certain glands(腺)in the birds’ bodies that may prepare them fo A. stopped migrating B. continued migrating C. stayed in the north D. migrated south and stayed there
[单项选择] Passage Five
One of the most strikingly apparent
instances of extrasensory perception is the precognitive experience, when a
person has a compelling perception of a coming disaster, news of death of a
loved one, or a communication from a long-lost friend, and the predicted event
then happens. Many who have had such experiences report that the emotional
intensity of the precognition and its subsequent verification provide an
overpowering sense of contact with another realm of reality. I have had such an
experience myself. Many years ago, I awoke in the middle of night in a cold
sweat, with a certain knowledge that a close relative had suddenly died. I was
so gripped with the haunting intensity of the experience that I was afraid to
place a long-distance phone call, (for fear that the relative would trip over
the telephone cord or something and m A. some kind of disaster a person experienced in his childhood B. a vague sense that something will happen and it does happen later C. the prediction of the death of a close friend D. uncertainty about an impending accident
[单项选择]Passage Five
One of Dara Torres’ trainers is walking all over me. Literally. I’m lying on my stomach as Steve Sierra concentrates his entire 160 lb. on my glutei and hamstrings. It hurts, but in a good way.
It’s all part of the flexibility--and strength-building regimen that Torres, who is making history, as the oldest swimmer to compete in the Olympics, credits with getting her 41-year-old body in good-enough shape to race athletes half her age. But resistance stretching, as it is called, is not just for the Olympians among us. Its focus on maximizing muscle flexibility has been useful for everyone from injured NBA players to children with cerebral palsy. The exercises may not look like much--they generally require no equipment other than a mat and maybe a towel and some straps--and they may not feel that strenuous, but you know the next day that you’ve had a workout.
Resistance stretching centers on flexing your muscles even as you stretch them; for example, inst A. live longer B. look attractive C. physically active D. rid of disease
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