that在主语从句中什么情况可以放在句首

Question

that在主语从句中什么情况可以放在句首

Answer 1

我认为楼主问的是 that从句作主语时 也就是充当主语从句时 主语从句是放前面 还是放后面.这和that的用法无关.that引导主语从句 that当然是在从句前 并且不能省.
that从句作主语时经常放在后面 而用it作形式主语.如
that the earth turns around the sun is known to all.地球绕太阳转这一点是众所周知的
= it is known to all that the earth turns around the sun.
that从句作主语 放在前面 显得头重脚轻 故 经常用it作形式主语 而把真主语that从句置后.
再如：it is a pity that he has made such a foolish mistake.
总之 that从句作主语 放前 放后都可以,最好放后 避免头重脚轻.