obligatory ·adjective (REQUIRED)

街道上排列着用于可回收垃圾的强制性蓝色垃圾桶。

The street was lined with the ___obligatory blue bins used for recyclable trash.

我认为这是一种很好的方式，鼓励人们学会喜欢锻炼，而不必因为它是强制性的而去做。

I think this is a very good way of encouraging people to learn to like exercise without them having to do it because it is ___obligatory.

在大多数州，系安全带是法律规定的强制性要求。

Wearing a seatbelt is ___obligatory by law in most states.