单项选择题

The most crucial problem any economic system faces is how to use its scarce resources.

A．puzzling
B．difficult
C．terrifying
D．urgent
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单项选择题
It is out of the question that the inspector will come .tomorrow.
A．impossible
B．possible
C．probable
D．likely
单项选择题
Medicine depends on other fields for basic information, particularly some of their specialized branches.
A．conventionally
B．obviously
C．especially
D．inevitably
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