常用不定式作主语的句型：Itis/was+名词+todosth.Itis/was+形容词(+forsb./ofsb.)+todosth.Ittakessb.sometimetodosth.•It'sourdutytotakegoodcareoftheold.•Itisdifficultforustofinishwritingthecompositioninanhour.•Ittakesmetwohourstofinishthework.常用动名词作主语的句型：Itis/was+nouse/goodnotanyuse/goodoflittleuse/goodworth+doingsth.•Itisnousecomplainingaboutsomethinginourdailyliferepeatedly.•Itisnogoodspeakingillofothers.•Itisworthmakinganappointmentbeforeyougo.
