单项选择题

The third paragraph is mainly about ______.

A．the harmful effects of chlorofluorocarbons on the environment
B．the necessity to ensure the environmental compatibility of new chemical substances
C．the economic feasibility of new chemical substances
D．the objective assessment of the progress in chemistry
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单项选择题
According to the passage, which of the following is a true statement, about sectional conflicts in America between 1763 and 1789
A．There conflicts were instigated by eastern interests against western settlers.
B．These conflicts were the most serious kind of conflict in America.
C．The conflicts eventually led to openly expressed class antagonism.
D．These conflicts contained an clement of class hostility.
单项选择题
According to the passage, Loyalism during the American Revolutionary War served the function of ______.
A．eliminating the disputes that existed among those colonists who supported the rebel cause
B．drawing upper, as opposed to lower, socioeconomic classes away from the rebel cause
C．tolerating the kinds of socioeconomic discontent that were not allowed to exist on the rebel side
D．absorbing members of socioeconomic groups on the rebel side who felt themselves in contention with members of other socioeconomic groups
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