单项选择题

Scientists believe that when life on earth began, the earth atmosphere consisted of ___________.

A．oxygen and nitrogen
B．hydrogen, oxygen and nitrogen
C．hydrogen and its compounds
D．hydrogen, oxygen and their compounds
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单项选择题
If a company wants its new pay structure to be successful, it is necessary to __________.
A．give the workers extra pay to encourage them
B．share the same opinion between the Trade Union and the employers
C．consult some problems associated with pay
D．adopt a special way to evaluate the performance of its employees
单项选择题
It can be inferred from the passage that __________.
A．the problem of prejudice and discrimination in the U.S. will be solved soon
B．blacks are free people now, so they can enjoy equal rights as whites
C．prejudice and discrimination are more severe in the South than in the North
D．now there are more blacks living in the North than in the South
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