1、必须英文：necessary，英 [?nes?s?ri] 美 [?nes?seri]。

2、加上必须的备课在内，我每天工作12个小时。With all the lesson preparation I have to do I work 12 hours a day.

3、他们很可能只想干他们必须的所有打扫烟囱的危险工作，从中获取额外报酬。Possibly they want danger money for all the chimney work they have to do.