今日短语：
be obliged to.

不得不…… (to之后接动词原形)；感激某人(to后面接名词)

例句：
Because of the heavy rain, we were obliged to stay at home.
由于下大雨，我们不得不留在家里。
We are very much obliged to you for your help.
我们非常感激你的帮助。