1。insist doing和insist on doing有什么不同么？还是没有insist doing这种说法的？ 2。It's unusual that David _____(come) here an hour ealier.答案是should come，为什么不是came，是虚拟语气么？但是应该怎么翻译这句话？ 3。teacher ban students_____(copy)home working. copying or from copying? 4.she devoted her whole life_(dovete)poor children in her country. devoting or to devoting? 5 the boy is considered _____(set)a good example to his classmates. to have set or having set? 请懂的朋友给我解释一下这几个题目好么？