1.必须英文:necessary,英 [ˈnesəsəri] 美 [ˈnesəseri]。
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.