现在完成时的标志词和用法，时态的核心是动词
定义：1.过去发生的动作对现在有影响
例如:She has cut her hair.
2.动作从过去延续到现在，可能还要持续下去
例如：He has worked here for5 months.
标志词：
already（肯定）
yet（否定/ 疑问）
just, before, recently, still, lately, never, ever, never, twice
on several occasion
in the past/ last few days/ weeks/ months/ years
(up to) these few days/ weeks/ months/ years
this morning/ week/ month/ year
up to present/ now
so far
till now
since + 时间
肯定句：
He/she/it+has+过去分词
You/We/They+have+过去分词
否定句：
He/she/it+hasn't+过去分词
You/We/They+haven't+过去分词
疑问句：
Have/has+主语+过去分词？
最后，牢记时态的方法就是多做题
