一、 一般现在时和现在进行时:
一般现在时表示的动作的时间不受限制或不确定,现在进行时表示动作的短暂性或有限度的持续性。请比较:
① Father works 48 hours every week.(指长期性的工作)
Don’t make a noise. Father is working. (指目前的工作)
② I usually wear sports shoes.(经常性的动作)
I’m not wearing sports shoes today. (暂时的情况)
瞬间动词用于进行时表示动作的重复,用于一般现在时表示动作的短暂性。如:
① The boy is jumping with joy.(那孩子高兴地跳了起来)
② Jack shoots for the goal.(杰克射门)
二、 一般过去时与现在完成时:
一般过去时不涉及对现在的影响,动作一般也不能延续。试比较:
His sister was in the school for eight years.(现在已不在学校)
His sister has been in the school for eight years.(现在还在学校)
一般过去时的时间状语只指过去而不涉及现在,但现在完成时常与不确定的或包括现在在内的时间状语连用。如:
The man was in prison in 1932.(具体的过去时间)
He has been in prison since 1932.(从过去到现在)
有些时间状语this morning, for a year等, 既可以用于一般过去时,又可用于现在完成时,但在意义上差别很大。如:
I ate two eggs this morning.(说话时是早晨以后)
I have eaten two eggs this morning.(说话时仍是早晨)
She learned English for 6 years.(动作已经过去)
She has learned English for 6 years.(动作刚结束或还在继续)