问题

It is not until recently ______ thescientists have found proof of there being water on Mars

A:couldn’t
B:needn’t
C:shouldn’t
D:mustn’t

正确答案是：

同类题型

Where is your sister—She ________ my mom with cooking.

The accident that happened at an oil field_____ the southeast coast of the USA has caused great damage to the environment.[ ]

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We have to stay at home ________ the heavy rain.

What time do you expect her________