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

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...