[单项选择]Caterpillars off all species produce an identical hormone called "juvenile hormone" that maintains feeding behavior. Only when a caterpillar has grown to the right size for pupation to take place does a special enzyme halt the production of juvenile hormone. This enzyme can be synthesized and will, on being ingested by immature caterpillars, kill them by stopping them from feeding.
Which of the following, if true, most strongly supports the view that it would not be advisable to try to eradicate agricultural pests that go through a caterpillar stage by spraying croplands with the enzyme mentioned above
A. Most species of caterpillar are subject to some natural predation.
B. Many agricultural pests do not go through a caterpillar stage.
C. Many agriculturally beneficial insects go through a caterpillar stage.
D. Since caterpillars of different species emerge at different times, several sprayings would be necessary.
E. (E) Although the enzyme has been synthesized in the laboratory, no large-scale production facilities exist as yet.

[填空题]Like all animal species, plant species must spread their offspring to suitable areas
where they can grow and pass on their parent’s genes. Young animals generally spread (1) ______
by walking or flying. Because plants don’t have that ability, they may somehow (2) ______
hitchhike. Some plant seeds scatter by blowing in the wind or floating on water.
Many other plant species, though, trick an animal into carrying their seeds. How do
they do They enclose them within a tasty fruit and advertise the fruit’s ripeness by
its color or smell. The hungry animal collects and swallows the fruit, walks or
flies off, but later spits out the seeds somewhere far from its parent tree. Seeds (3) ______
can thereby be carried thousands of miles. It may surprise you to learn that plant (4) ______
seeds can resist digestion. In fact, some seeds actually require passage through an
animal’s body before they can grow. Wild strawberries offer a good example of

[单项选择]For what purpose does the pilot shut off all the engines
A. To find out exactly what happens.
B. To save fuel to fly longer.
C. To find out where the big stone is.
D. To fly even more slowly.

[填空题]On new year’s eve, fireworks went off all over the city, adding gaiety to the festival.

[单项选择]Future education needs to produce graduates of all the following categories EXCEPT
A. those who can adapt to different professions.
B. those who have a high flexibility of mind.
C. those who are thinkers, historians and philosophers.
D. those who possess only highly specialized skills.

[单项选择]

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A. By purchasing a particular item in the store
B. By buying any other item on the shelves
C. By attending a special sales promotion
D. By visiting the store during the fall