如果你碰巧见到彼得，代我向他问好。

If you ___happen ___to see Peter, say "hi" for me.

你该不会正好知道她的电话号码吧？

You don't ___happen ___to know her phone number, do you?

我现在能理解我偶然读到的任何英文内容。

I can understand whatever I ___happen ___to read in English now.