The cleaners must prevent the street .
A. getting dirty
B. from dirty
C. from get dirty
D. from getting dirty
网友回答
A. getting dirty
B. from dirty
C. from get dirty
(答案→)D. from getting dirty
解析：prevent sb from doing sth预防，阻止某人干某事，from是介词后面接名词或者动名词。故选D，清洁工必须防止大街变脏。