我在超市购物时意外遇到了多年未见的老同学。

I ___encountered an old classmate I hadn't seen for years while shopping at the supermarket.

旅行时我们经常遇到语言障碍。

We often ___encounter language barriers when traveling.

他们在巷子里偶然遭遇了敌对帮派。

They unexpectedly ___encountered a rival gang in the alley.