1.现在时 (1)现在完成时用来表示对目前状况仍有影响的，刚刚完成的动作(常与yet，already，just连用)，或者过去某一时刻发生的，持续到现在的情况(常与for，since连用)现在完成时词。例如： 1)I have just finished my homework. 2)Mary has been ill for three days. (2)常与现在完成时连用的时间状语有：since, for, during, over等引导出的短语；副词already, yet, just, ever, now, before, often, lately, recently等；状语词组this week (morning, month, year), so far, up to now, many times, up to the present等。例如： 1)I haven’t been there for five years. 2)So far, she hasn’t enjoyed the summer vacation. 3)There have been a lot of changes since 1978. (3)完成时态可用在下列结构中： This (That, It) is (was) the first (second…) time +定语从句；This (That, It) is (was) the only (last) + n +定语从句；This (That, It) is (was) +形容词最高级+ n +定语从句。如果主句的谓语动词是一般现在时，从句的谓语动词通常用现在完成时；如果主句谓语动词是一般过去时，从句谓语动词通常用过去完成时。例如： (1)This is one of the rarest questions that have ever been raised at such a meeting. (2)There was a knock at the door. It was the second time someone had interrupted me that evening. already(已经）【通常不放在句尾】,yet（已经）,for,before,ever（曾经）,never（从未）,so far（到目前为止）,since(从……时候） for+一段时间 如：one year（一年） ,two month(两个月）而since+时间点 如：one year ago(一年之前） 表示的是一个具体的时间，例如今天是09年8月1日，它指的就是具体的08年8月1日。 *完成时的定语从句 since引导的定语从句主句用完成时，后面的从句一定要用一般过去时。例如：He hadn’t been back there since he finished high school. 从他中学毕业后他就没有回去过那里。 since后面的句子没有had，直接用过去式，而主句则用的过去完成时。
