单项选择题

Experiments in the photography of moving objects （） in both the united states and Europe before 1990.

A．have been conducting
B．were conducting
C．had been conducted
D．are conducted

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单项选择题
（） have come up with the solutions to the problem.

A．The boy student
B．The boys student
C．The boy students
D．The boys sutdents
单项选择题
She （） in the feet on her way home from work.

A．was hurting
B．is hurt
C．hurts
D．got hurt
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