It was not until last week--she found--she thought was quite

1.首先是it is/was...that...的强调句句型,强调时间：last week.这种句型的特点是如果把it is/was...that...省去,原句意思/结构不变,仍然是完整的句子.
2.然后,what是作为thought的宾语出现的.正句句子的成分分解为she found [（what she thought） was quite mistaken].[]中的是she found的宾语从句,（）中的是was quite mistaken主语从句,what表示“她认为”的内容
再问： 第二个空考的是主语从句缺宾语用what是吗