Question

【题目】Something must be done to prevent factories ________ poisonous gases so as to keep the city ________.

sending out; from polluting

send out; polluting

from sending out; from polluting

sending out; being polluted

Answer 1

【答案】D

【解析】keep/prevent/stop…from doing sth.都表示“阻止做某事”，其中keep…from doing sth.中的from不能省略，动词后的宾语和from后的动名词是被动关系时，要用动名词的被动形式。