单项选择题

It is desirable that water used for drinking （） pure.

A. were
B. should be
C. is
D. ought to be

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单项选择题
No one knows whether a child's （） towards fatness is inherited or due to the food he eats.

A. tendency
B. trend
C. intention
D. inclination
单项选择题
A series of attempts （） made, he came to a successful solution to the problem.

A. to be
B. had been
C. were
D. having been
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