be careful where的用法和樣例：
例句
- She always wants to be the focus of attention.
她老想成為人們注意的中心。 - Be careful, the onion shouldn't turn brown.
注意，別把洋蔥燒焦。 - Be on the watch for thieves in this crowd.
提防人群中有小偷。 - Be sure to be watchful or alert.
必須留神，千萬要提防。 - You should be careful when making a promise.
你應當謹慎做出承諾。 - But I'm trying to be a little canny about it.
但是我想對此謹慎一些。
