单项选择题

A．more and more wild chimpanzees are being slaughteredB……

The biggest worry that the researchers now have is _______.

A．more and more wild chimpanzees are being slaughtered
B．AIDS virus is difficult to be killed and controlled
C．it is not easy to repair people’s deficient immune systems
D．many dangerous viruses are being transmitted to humans

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单项选择题The reason some children are backward in speaking is most probably that _______.

A．they are incapable of learning language rapidly
B．they are exposed to too much language of once
C．their mothers respond inadequately to their attempts to speak
D．their mothers are not intelligent enough to help them

单项选择题Many AIDS experts are not completely satisfied with results of the study because _______.

A．only a limited number of chimpanzees are used for sampling the virus
B．it is now extremely difficult to find chimpanzees that carry the virus
C．the samples collected are from two different subspecies of chimpanzees
D．it does not provide reliable evidence of the link between SIV and HIV-I

单项选择题What is exceptionally remarkable about a child is that ______.

A．he is born with the capacity to speak
B．he has a brain more complex than an animal's
C．he can produce his own sentences
D．he owes his speech ability to good nursing

单项选择题The purpose of Frederick I's experiment was _______.

A．to prove that children are born with the ability to speak
B．to discover what language a child would speak without hearing any human speech
C．to find out what role careful nursing would play in teaching a child to speak
D．to prove that a child could be damaged without learning a language

单项选择题Which of the following can NOT be inferred from the passage

A．The faculty of speech is inborn in man.
B．Encouragement is anything but essential to a child in language learning.
C．The child's brain is highly selective.
D．Most children learn their language in definite stages.