seem to be doing sth ,seem to do ,seem to have done sth

题目

seem to be doing sth ,seem to do ,seem to have done sth
这三者有什么区别,

答案

seem to be doing sth表示不定式的动作和主句中seem是同一个时态,比如,He seems to be doing his homework.他好像正在做作业；seem to do 表示不定式的动作发生在主句动词seem之后,比如It seems to rain.好像要下雨...