a lucky guess的用法和样例：
- Mr. Knightley: Triumph? You made a lucky guess!
- He didn't really know the answers. He just made a lucky guess.
- It was, but Cai Yong suspected that his daughter had just made a lucky guess.
- Whew! That car was a lucky escape.
- I seem to be having a lucky streak.
- considered himself lucky that the tornado missed his house; a lucky guess.