prevent/stop/keep… from doing…这三个句式的意义都是“阻止……做……或阻止某事的发生”,而protect…from/against…表示“保护……免受……prevent/stop/keep... from doing..表示“阻止某人做某事”例如:We must prevent the water from being polluted. What stopped him from coming here.protect…from/against…表示“保护……免受……”例如:Protect children from violence 保护儿童免遭暴力侵犯。