① come about意為“發(fā)生,造成”,為不及物短語動詞,不能用于被動語態(tài),主語只能是事物,不能是人。
How did the accident come about?事故是怎樣發(fā)生的?
How did the bad situation come about?這種不利的局面是怎樣造成的?
② come across意為“無意中發(fā)現(xiàn),偶然遇見,突然出現(xiàn)”,也可表示“越過,穿過”,為及物性短語動詞,主語可以是人,也可以是物,賓語也可以是人或物。
I came across this pen when I was looking for something else. 我在找別的東西時,無意中發(fā)現(xiàn)了這支鋼筆。
She came across an old friend in the street this morning. 她今天上午在街上偶然遇到一位老朋友。
An idea suddenly came across my mind. 我突然想起一個主意。
They came across the hill by car. 他們乘車越過那座小山。
He came across the street to the bookstore. 他穿過大街來到那家書店。
③ come from可以表示:①是什么地方人,②出身于什么家庭,③從什么地方來。
Where does he come from?他是什么地方人?(一般現(xiàn)在時,表示籍貫)
Where did he come from?他從什么地方來?(一般過去時,表示過去的動作)
She comes from/of a worker's family. 她出身于工人家庭。