单项选择题

The professor, ________whether anyone would come to help him, had to prepare for the experiment by himself.

A．did not know
B．having not known
C．had not known
D．not knowing
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单项选择题
I was surprised that no one ________them of the danger.
A．warns
B．warned
C．has warned
D．had warned
单项选择题
Alice is going to the photographer’s this afternoon ________.
A．to have taken her photograph
B．to have her photograph taken
C．to have her photograph being taken
D．to have her photograph been taken
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