捏个 我是个英语菜鸟 我们必须尽最大努力阻止河流污染 用英语怎么说?

We must try our best to prevent the river from being polluted.
We must try our best to stop river pollutions.
花时间做某事,不适合用在这个句子上
spend time doing something
I spent five hours doing my homework last Sunday.
I spent five hours on my homework last Sunday.
上周日我用了五个小时做作业.

answer 1:"we must do our best to stop river pollution".
answer2:"spend time to do something"花费时间去做某事
or "spend time doing something" 花费时间正在做某事

We must try our best to stop/prevent the river from pollution.
Sb spend(s) some time doing sth 某人花一些时间做某事

We must try our best to prevent the river been polluted.
sb. spend sometime in doing sth.