...意思，为什么还有用when？岂不是误人子弟！虽然主从句时态告诉了我们。原句：3、By then, however, in many places the grass had already taken root. In place of the great trees which had been growing there for centuries patc...
...而推测出来的情况，所以主句通常需要情态动词（或将来时态）。如： If you move, I’ll shoot you.If it rains, the match will be cancelled.If I press this button, what will happen? 这类句子中，从句也可能是现在完成时或现在进行时。I will retu...
...1.
构成方法被动语态由“助动词be+过去分词”构成。不同时态的被动语态如下表： 2.
用法举例Football
is played all over the world. 全世界都有人踢足球。Rome was
not built in a day. 罗马不是一天建成的。He will be
asked to speak at the meeting. 他...
...致（3）有be动词，这个be动词可以是系动词，可以是进行时态的be，也可以是被动语态的be。例如：Mary often helped her classmates when (she was) free. （was是系动词）While (you were) walking the dog, you were careless. （were是进行时的助动词）John won'...
...lunch. 我真的希望你留下吃午饭。用于表示强调的do可以有时态的变化，但其后的动词要用原形。如：He does look tired. 他确实显得很疲倦。He
did come but soon went back. 他的确来过，但很快就回去了。She did write to say
thank you. 她的确写信...
...表示将来的能力：通常不用can或could，而用be able to的将来时态。如：I’ll
be able to speak French in another few months. 再过几个月我就会讲法语了。但是，若表示现在决定将来是否有能力做某事，则可用 can。如：I haven’t got time
today, but ...