That they were wrong in these matters (is/are)?now clear to us all.

问题描述:

That they were wrong in these matters (is/are)?now clear to us all.
为什么啊

当然填is了,原因:在英语中,句子作主语,谓语动词用三单
That they were wrong in these matters是原句子的主语 is是谓语动词