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Despite their numerous attempts to do so, scientists have not been able to sustain a controlled nuclear fusion reaction.
A their numerous attempts to do so, scientists have not been able to
B their numerous attempts to do it, scientists have not been able to
C them numerously attempting to do so, scientists have not been able to
D their numerously attempting to do so, scientists cannot
E their numerous attempt to do so, scientists were not able to
正确答案是A,我选的是E, 我就想请问一下为什么这里不能用were 呀?谢谢啦
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