it的所有用法总结全部答:②It+be+adj(easy,safe,common,normal ?)+forsbtodosth 该句型中adj若为important,necessary,natural,possible,strange,vital,essential等可改为从句,从句用should+动词原形。.Eg:It’sverydangerousforchildrentoplaywithfire.ItisimportantforustolearnEnglishwell.(=Itisimportantthatwe(should)learnEnglish...