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。
