一道语法题
问题描述：
一道语法题
Madame Curies is believed ________ the radium.A discovering B.having discovered C.to have discovered D.to discover
正确答案是C
为什么不可以选B?非谓语动词having done 不是也是表示动作在主语谓语动词之前吗?
答
当动词believe被用作被动语态时,需要用be believed to do.这个句子的主动形式应该是(we /someone) believe that Madame Curies discovered the radium.改成被动就成了Madame Curies is believed to discover the radium( by us ).