主语从句中that要充当成分吗?

两个句子中that 都不做成分!都是引导主语从句的连词.只是第二句写的不太正确,应该是That the seas are being overfished has been known for years.
这样才算一个完整的主语the seas are being overfished 加上that 就变成了从句,因为一个句子中只有一个谓语,所以前面的要加that,
不懂的话,可以把他们换成it引导的句子
为了防止句子头重脚轻,通常把形式主语it放在句首位置,真正主语搁置于句末
it is a miracle that she survived from the accident.
it has been known for years that the seas being overfished.
光是the seas are being overfished 不能作主语,因为本身是一个独立句子了,只能做从句.
本身的主语是the seas.放在原句里面如果没有引导的that,语法错.
the seas are being overfished.结构是个 进行时的被动语态句子.