单项选择题

Every device______ in the spacecraft must be designed and made with great care so as to be sure that nothing goes wrong in operation.

A．to be fitted
B．fitted
C．fitting
D．to have been fitted
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单项选择题
Mr. Jones, I am really pleased______ you. And I hope we will be able to see each other in not long time.
A．to meet
B．to have met
C．at meeting
D．having met
单项选择题
There are many kinds of synthetic materials,______ plastics are the most common.
A．between which
B．of which
C．in which
D．among which
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