he explained how it was that hewas still alive 我知道it是形式主语 that后边是真的主语但是我还有问题

he explained how it was that hewas still alive 我知道it是形式主语 that后边是真的主语但是我还有问题

主语：He 谓语：explained
宾语（从句）：how it was that he was still alive. 既是宾语从句并且是一个强调句,
句式为：how he was still alive,意思是,“他是怎样活下来的.”但是特殊疑问句改为强调句：疑问词如why+is/was it +that +其它，如果这个特殊疑问句要做宾语从句，那么只需把is/was和 it的位置调就行了，就像陈述语序一样。

这里的it是引导强调句，强调句的形式：it is/was+被强调部分+that+句子的剩余部分.
how在强调句中的正常位置是：how was it that he was still alive.但在explained后当宾语，其从句的顺序就是：he explained how it was that he was still alive.这句话如果不是强调句，去掉强调句的结构：it is/was+被强调部分+that.....，它的顺序是：How he was still alive.---He explained how he was still alive.
大意：他解释他是如何还活着的原因。

it是that引导的句子的形式主语。正常的语序是 thathe was still alive was how, that 从句后置了，前面加个形式主语it

可以看成：
He explained (how it was) that he was still alive.
这句话是宾语从句，他解释他是如何还活着的。
关于it，应该是 it was that he was still alive.