prevent sb. doing sth.\stop sb. from doing sth\keep sb from doing sth\protect sb from doing sth的区别

prevent...from, keep...from还有stop。。。from 这三个句式的意义都是：阻止。。。做。。。或阻止某事的发生，而protect...from是表示保护。。。不受伤害from后接能带来伤害或损害之物。

You should protect the children from catching cold.  你应该防备孩子们受凉。

prevent...from, keep...from还有stop。。。from 这三个句式中from后面的动词与from前面的词构成动宾关系时，后面用动名词的被动形式。

We must prevent the water from being polluted.

What stopped him from coming here.

The heavy rain kept us from coming on time.

I am sorry to have kept you waiting.

You had better wear sunglasses to protect your eyes from the sun.

prevent sb from doing sth与stop sb from doing sth用法相同，在主动语态中from可以省略，被动语态中不行keep...from在表示此意时，from不可以省略。keep。。。doing 是使。。处在。。状态中的意思。这样想一想，如果没有了from就变成了keep sb doing sth了，意思就反过来了。