keep/stop/prevent...from doing意为“阻止/防止……做某事”，在主动语态中，stop 和prevent构成的两个短语中from可省略，但keep短语中的from不能省略。它们在被动语态中from都不可省略。如：[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ KPh?  X|-H6g;vvFroG]

    The Great Green Wall will stop the wind (from) blowing the earth away. 绿色长城将阻挡风把泥土刮走。[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ ;*/+/szgbx@FroG]

    We were stopped from going home by the heavy rain. 大雨阻止了我们回家。[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ C=VM%vpTd\w19FroG]