4.can could may must后接完成式的用法 (1)can could后接完成式的用法 在否定式或疑问句中,表示对过去发生过的事情的怀疑或不肯定的态度。如:Could he have said so?
在肯定句中,可以表示过去可能做到而实际并没做到的事情,有劝告或责备的语气。如:--When did you answer her letter?--Only yesterday.--It's too late.You could have answered it earlier,I am sure.
在肯定句中,可以表示过去可能做到而实际并没做到的事情,有劝告或责备的语气。如:--When did you answer her letter?--Only yesterday.--It's too late.You could have answered it earlier,I am sure.