常用不定式作主语的句型：Itis/was+名词+todosth
Itis/was+形容词(+forsb
)+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
