初中英语时态知识点：一般过去时三种变化技巧

　　一变：肯定句变为否定句

　　【技巧1】当句中含有情态动词或助动词could，would，should等时，可直接在其后面加not构成否定句。例如：

　　I could get you a concert ticket.I could not / couldnt get you a concert ticket.

　　【技巧2】当句中含有系动词was，were 时，可直接在其后加not构成否定句。例如：

　　I was on the Internet when you called me.I was not / wasnt on the Internet when you called me.

　　【技巧3】当句中谓语是除情态动词、助动词、系动词was,were以外的动词时，在该动词之前加did not / didnt，动词还原，构成否定句。例如：

　　The famous singer sang some Chinese songs.The famous singer did not / didnt sing any Chinese songs.

　　二变：陈述句变为一般疑问句

　　【技巧1】移动词语的位置。将was，were,could，would，should等移到句首。例如：

　　He could pack his things himself.Could he pack his things himself?

　　【技巧2】添加助动词did。谓语是除情态动词、助动词、系动词was,were以外的动词时，在主语之前加did，动词还原。例如：

　　Mr Li looked very old.Did Mr Li look very old?

　　三变：陈述句变为特殊疑问句