1
be obliged to do sth 不得不做某事,一定要做某事 =feel obliged to do sth
be not obliged to do 不是一定要(非要)做某事
2
one oblige another to do sth 某人迫使另外一人做某事
.not to do sth .迫使不让他做某事
be obliged to do sth 被迫做..
.not to do 被迫不能做...