我就以你給的句子為例來說明.
They said that he had gone abroad to study English．
在這個句子中he had gone abroad to study English是賓語從句,that 是先行詞,是陳述句時用來引導從句的.這個從句在句中充當賓語,賓語一般是由名詞或代詞.所以,這句話的被動形式就成了 That he had gone abroad to study English was said． 為了是句子各部分均衡,用it 代替從句就變?yōu)?It was said that he had gone abroad to study English．
而在英語中,一些表示“據(jù)說”或“相信”的動詞如believe,consider,expect,report,say,suppose,think等可以用于句型“It＋be＋過去分詞＋that從句”或“主語＋be＋過去分詞＋to do sth.”.
例如,It is said that the boy has passed the national exam.
＝The boy is said to have passed the national exam.
而你后面的那個句子,He told me the police had arrested the thief,只是把賓語部分變?yōu)榱吮粍有问?主句部分沒有發(fā)生改變,還是He told me .太感謝了，完全明白了。我還想問一下這句 People said that there was gold in that cave 變被動 為什么是變成 there was said to have been gold 變成 there was said to be gold 不行嗎？不是很理解這里的have been goldthere was said to have been gold
和你說的
there was said to be gold
這兩句區(qū)別只在后面的不定式，因為不定式本身含有未發(fā)生的，或動作前后相繼的意思，而且不定式里只能用動詞原形，所以要表示過去時態(tài)只能用 to have done 的形式了。那我是不是能這樣理解，一旦是過去式，或過完等，就要變成主語＋be＋過去分詞＋to have done呢？而不能直接用to do sth比如 people think that they found a book 變成they are thought to have found a book,而不能用they are thought to be find a book。這樣理解 對嗎？嗯，是這樣的。absolutely right！