.现在完成时的定义：1. 表示过去发生或已经完成的某一动作对现在造成的影响或结果e.g. Have you had your lunch yet?Yes, I have. Ive just had it. (现在我不饿了。)2. 表示动作或状态从过去某一时刻开始，一直延续到现在，而且可能还要继续下去。e.g. I havent seen her these days.Ive known Bob for three years.Ive been at this school for over two years.现在完成时的构成：主语+have/has +动词的过去分词.否定：have, has后面加not 一般疑问句：have, has提到主语前用法要点：1.现在完成时往往同表示不确定的过去时间状语连用already(肯定句中)，yet(否定，疑问，句末)，just, before, recently, still, lately, never等:现在完成时常用短语 up to now /till now, s
