The usage of the present perfect tense
The disappearance of Justin has made Kelly very unhappy. Justin的失踪让Kelly非常难过。( Justin在过去失踪,但是Kelly至今都在为他的失踪感到难过) 2. I have had my lunch. 我已经吃过午饭了。(过去吃了,现在不饿。)
动作或状态发生在过去,但仍然对现在产生影响。
3. I have not seen Justin since last Friday night. 从上周五晚上到现在一直都没有见到过Justin。(到现在还没有见到) The police have not found Justin since his disappearance. 从Justin失踪到现在警察一直没找到他。 (至今还没有找到)
过去开始的动作一直延续到现在,并对现在产生影响。