单项选择题

These compounds could not have been formed if the chemical reaction ______ stopped.

A．have been
B．has been
C．had been
D．were
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单项选择题
The old man and his dog were ______ to each other.
A．supported
B．helped
C．relied
D．devoted
单项选择题
The train was late ______ the heavy snowstorm.
A．as a result of
B．in case of
C．with the relation to
D．by way of
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