it is said that that was how the chinese first raised silk worms
问题描述：
it is said that that was how the chinese first raised silk worms
答
句子结构是这样的：it was...that,这里的it是形式主语,其实这句话是主语从句,真正的主语是that that was how the chinese first raised silkworms.其次,在这句主语从句中,又套了一句表语从句,这句表语从句的主语是第...