现在完成时现在完成时的构成：现在完成时由助动词havehas + 过去分词构成，第三人称单数用has，其余用have。I have been in Shenzhen for seven years.Lily hasnt been to America before.现在完成时的用法：1）现在完成时通常表示在说话之前已经完成的动作或存在的状态。说话人强调的是该动作或状态对现在的结果或影响。My daughter has just gone out. 我女儿刚出去。Im sure weve met before. 我肯定我们以前见过面。She has arrived. 她到了。2）表示持续到现在的动作或状态, for, since,yet等。如：I havent heard from her these days. 这些日子我没有收到她的信。We havent seen you recently. 最近我们没有见到你。They have been away for two years. 他们离开已经两年了。S
