oblige v<正式>非做…不可，迫使。
(辨析)指因法律、义务、形势等关系而不得不做某事，通常用被动语态。
(例证)He was obliged to tell the truth.
他被迫讲出了实情。
Poverty obliged her to live a hard life.
贫困迫使她过艰苦的生活。
The law obliges parents to send their children to.school.
法律强制父母送子女入学。
have to modal v.必须，不得不。
(辨析)指客观情况迫使某人做某事，侧重于客观上的“必须”。
(例证) Did she have to pay a fine?
她非得交罚款吗？
I have to admit that the idea of marriage scares me.
我不得不承认，一想到结婚我就害怕。
must modal v.必须。
(辨析)指因需要、命令或强制而必得做某事，侧重于主观上的“必须”。
(例证) We must take action at once.
我们必须立即采取行动。
I think we must reduce our prices or spend more money on advertising.
我认为我们必须降低价格，或者是在广告上花更多的钱。
