I can't stand people throwing litter about.

我不能忍受人们乱丢垃圾。

We shouldn't spit in public places or throw litter about.

我们不应该在公众场合随地吐痰，乱丢垃圾。

You must not throw litter about.

别到处乱扔垃圾。

Don't throw litter about.

别到处乱扔垃圾。

Don't leave litter about in public places.

不要在公共场所到处乱扔垃圾。