问几道英语语法题目

问几道英语语法题目
1.it was not until ___ the problem difficult to work out that i decided to ask tom for advice.为什么不用did i find要用i did find
2.it remains__whether jim'll be fit enough to play in the finals
选项是to be seen 为什么要用被动而不是to see
3.i ___ in london for many years ,but i've never regretted my final decision to move back to china.
有for many years了 为什么不用had lived 而是lived
4.the moment the 28th olympic games ___ open, the whole world cheered为什么是were declared而不是declared
5.while she was combing her hair ,__,breaking to pieces
答案是down fell the mirror 我选了down did the mirror fall
这种题目有什么规律的吗?
jim’ll = jim will