三题答案该如何选,英语高手请进1.Whenhegotoffthebus,ithappende.A.torainB.toberaingingC.rainingD.toraining为什么选B而不A或是C2.Thebirdwasluckythatitjustmissed.A.catchingB.tobecaughtC.beingcaught

Question

三题答案该如何选,英语高手请进
1.When he got off the bus,it happende_____.
A.to rain B.to be rainging C.raining D.to raining
为什么选B而不A或是C
2.The bird was lucky that it just missed______.
A.catching B.to be caught C.being caught D.to catch
为什么C而不选A
3.It was polite for the young ____theri seats to the old.
A.giving up B.to give up C.being given up D.to be given up
为什么选B而不选C
我个人感觉自己可能是关于动词不定式与动名词的用法有点搞晕了,上面三题有点没太弄明白,希望高手能给一些指导,

Answer 1

1：it happens to do sth 碰巧发生什么事
这句话的意思是,当他下车的时候,正巧在下雨.强调那个状态,所以填进行时比较恰当.
2：miss doing sth 错过做某事,小鸟与抓是被动关系,当然用被动态.
3:it is +adj.for sb to do sth 固定用法,年轻人让座给老人,明显用主动态