单项选择题

It is thus of exceptional importance ______ extinction theories, but until now problems with dating have limited its potential.

A．for a testing purpose on
B．as a testing reason in
C．as a testing ground for
D．for some useful ends of
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单项选择题
This, they say, is proof that the more primitive species was not simply supplanted by an advanced one ______ into one.
A．but also developed
B．but reformed sharply
C．but merely turned
D．but evolved slowly
单项选择题
Which of the following is NOT the reason why depression has no apparent survival benefits for us today
A．We live in relatively affluent society.
B．The environment is not as harsh and rough as it was for our ancestors.
C．Our depression is mainly caused by the action of other people not the environment.
D．We seldom suffer from depression and frustration nowadays.
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