单项选择题

Which of the following is TRUE of CF echoes

A．They enable the bat to determine the size of the target.
B．They help identify the range of widely spaced targets.
C．In some species, they enable the bat to judge whether it is closing in on its target.
D．In some species, they help the bat to tell the shape of the target.

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单项选择题

According to the passage, which of the following statements is CORRECT

A．Discrimination against people with AIDS is declining.
B．Homosexuals have been harassed [or being possible HIV carriers.
C．HIV is transmitted through physical contact of any sort.
D．The fear of AIDS will inevitably change people's sexual behavior.

单项选择题

If the argument in the passage is valid, taboos against eating in-the presence of others who are NOT also eating would be LEAST likely in a society that ______.

A．always had a plentiful supply of food
B．emphasized the need to share worldly goods
C．emphasized the value of privacy
D．discouraged overindulgence