did xiao yang come？

　　how many people have gone to the factory？

　　how many people went to the factory？

　　we haven't invited him. we didn't invite him.有时同样一个动作，也随着说话的意图不同而用不同时态表示：has he gone to town？ how did he go there？ 后一句谈动作本身，与现在无联系。

　　have you had your lunch？ where did you have it？ 你吃中午饭了吗？在那吃的？

　　has she left？ why did she leave so early？

　　某些动词的现在完成时刻表示一直持续到现在的状态：how have you been （recently）？

　　the conference has lasted five days. we've known each other since we were children.特别是动词be，是常常这样用的：he's been back for three days. （不能用has come back）

　　she has been a teacher for ten years. （不能说has become）

　　he has been in college for a year. （不能说has entered）

　　由于come， become， enter和get up 等动词都只代表一个短暂的动作，不能代表一个延续的状态，这是需要用be来表示延续的状态：另外有少数动词（主要是work， study， teach， live等）可用于现在完成时表示一直持续到现在的一个动作：how long have you worked here？

　　she has taught english for many years. we've lived here for quite a few years.但大多数动词不宜这样用，而需用现在完成进行时。

　　注：have been （to）长可用来表示“到过某地”或“刚去做过某事”

　　have you ever been to xi'an？

　　xiao liu has just been here. we've been here（there）many times. l 现在完成时还可用在表示时间或条件的状语从句中，表示将来某时业已完成的动作：i'll go and see the exhibition as soon as i have got the recorder fixed. we'll start at five o'clock if it has stopped raining by then i will gibe my opinion when i have read the book through.这利用“现在完成时”时表示这动作将在另一动作之前完成。如果两个动词同时发生，或几乎同时发生，（也就是说一个动作紧接着另一个动作），一般就不用这个时态：i'll let you know as soon as i hear from her. she'll write you when she gets there.在这样的情况下（特别是当我们用的是get， arrive， see， hear， leave， return 等代表迅即完成的动作的动词时），多用一般现在时。有时两种时态都可以用：we'll leave as soon as it stops（has stopped） raining. i'll tell him after you leave （have left）。

　　注：have got 形式上时现在完成时，却和have时同一个意思：she has got （=has） a slight temperature. have you got （=do you have） any sisters？

　　另外，现在有一种倾向，特别是在美国，在随便谈话时，常用一般过去时代替现在完成时：i saw it already （=i have seen it already）。

　　did you return the records yet （=have you returned the records yet）？

　　i just come back （=i've just come back）。