单项选择题

______ experiments on the laboratory, it started to rain heavily.

A．While performing
B．Performing
C．While I was performing
D．To perform

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单项选择题

______finished his work, he had to stay at home at the weekend.

A．Having not been
B．Being not
C．Not having
D．Having not

单项选择题

I like to get up early so that I can get plenty of work ______ before lunch.

A．to do
B．doing
C．done
D．being done

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