阻止某人做某事的4种用法

如下：

stop sb tfrom doing sth。

prevent sb from doing sth。

keep sb from doing sth。

补充：

 因为 stop sb. (from) doing sth 和 prevent sb (from) doing sth 省掉了from 不会影响语义，而 keep sb. from doing sth 省掉from后，意思正好相反：

I kept him working on his homework —— 我一直让他做作业。

I kept him from working on his homework —— 我不让他做作业。

4.discourage sb from doing sth。