从定义上来讲的话,现在完成时是指过去做过,对现在还有影响的事过去式指单纯过去做了的事。现在完成时常与ever , already, yet , still ,for .since连用当与for , since连用时, 句子里的谓动要用延续性动词还有就是,当句子中有明显的过去时间状语,就一定要用过去式e.g : I did some shopping yesterday afternoon.而不能说
I have done some shopping yesterday afternoon....