The water companies were instructed to keep the people to the polluted water.A. from expo

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A. from exposing
B. being exposed
C. exposing
(答案→)D. from being exposed
解析：这题考察词组：keep sb from doing“阻止某人做”，这里的from不能省略，另外be exposed to“暴露于”，句意是：水厂被指示不能让人们接触到污染的水。选D。