1. Stop sb. from doing sth.停止...做什么(已经在做了，要停止)
The teacher wants to stop her students from jumping on the tables.
2. Prevent sb. from doing sth. 防止...做什么(还没有做，为了预防为主)
The teacher put a mat on the floor to prevent students from hurting themselves.
3. Keep sb from doing sth. 制止...做。。。
以上结构中，keep句型不可省略from, 在被动句中都不可省略from.
4 Protect sb. from ...
Protect sb. from being ...保护...
We should protect ourselves from scams.
The manager wants to protect her secretary from being fired.
stop 即是停止的意思。例如，在红灯前将车停下来，就叫做：stop the car before traffic light turns red.
prevent 即是防止的意思。例如，to prevent accidents from happening, public should be more cautious of their own safety.
protect 即是保护的意思。例如，women should protect themselves from family violence by voicing out through newspapers.
