一、以形式主语it引导的句型。
句型1. It (so) happened（chanced）that +clause. = sb. happened /chanced to do sth. =sb.did sth.by chance.
如： It happened that he was out when I got there. 当我到那儿时，碰巧他不在。＝He happened to beout when I got there.= It chanced that he was out when I got there= He was out by chancewhen I got there.
