一般情况下,ago 常和一般过去时连用.不能与完成时连用。ago 必须和表示时间的词语连用。before 常与完成时连用。如:He left two weeks ago.他两周前离开了。(距现在)I had heard it three days before.我3天前听说过此事。(距当时)bef...
一、表示重量、度量、衡量、价值的复数名词作主语,谓语是静态(状态)动词时用单数形式(1—3例),是动态动词时则用复数形式(4—6例)。1.Five thousand kilometres is a good distance.2.Ten minutes seems an hour when one is waiting f...
Active American English下册第115课开始出现动词现在完成时。现在完成时的形式是助动词have+动词-ed分词。如: ①He has learned English for five months.(下p.183) ②How long have you known each other?(下,p.190) ③My father ha...