The hair and fur are made into mats and brooms and sent to 24 waters to absorb the oil.
答案：(C) polluted
過去分詞 polluted 作形容詞修飾 waters，「被污染的水域」；pollute（原形動詞，不能這樣修飾名詞）、polluting（現在分詞，主動語意方向不合）、pollution（名詞，不能這樣修飾另一個名詞）都不合。
看到 waters 帶著 -s 你可能先愣一下：water 不是不可數嗎？這裡的 waters 是「水域、海域」的意思，這個意思是可數的，例如 the waters of the Gulf of Mexico（墨西哥灣海域）。先確定 waters 是名詞，空格是修飾它的位置，這一格就解決一半了。
空格夾在介系詞 to 和名詞 waters 中間，這是形容詞的位置。分詞當形容詞要判斷主動還是被動：水是「被污染」的，不是水去污染別人，所以用過去分詞 polluted。還原成完整子句驗算：waters that have been polluted（已經被污染的水域），語意通順。反過來如果填 polluting，還原是 waters that are polluting something（正在污染別的東西的水域），跟後面 to absorb the oil（去吸走油污）的目的直接矛盾。國中學過的對照組可以整組搬過來：a broken window（被打破的窗戶，過去分詞表被動）對 a barking dog（正在吠的狗，現在分詞表主動）。
pollute 是原形動詞，動詞不能直接放在名詞前面當修飾語。pollution 是名詞，兩個名詞連用要看得出前者是後者的類別或用途，例如 water pollution（水污染）是通的，但 pollution waters 講不出合理的關係。polluting 的主被動方向相反，如上所述。
polluted waters（受污染的水域）、water pollution（水污染）、be made into（被製成……）、absorb（吸收）、soak up（吸收）、a broken window（被打破的窗戶）、a barking dog（正在吠的狗）、be sent to（被送到……）。
Hair usually gets greasy when it has not been washed because it soaks up oil—hence the need for shampoo! 21 this oil-absorbing feature might not always be so great for our hygiene, it can be great for the environment.
Matter of Trust, a nonprofit organization, has an innovative solution for removing the large-scale oil spill in the Gulf of Mexico in 2010, using the ultimate renewable 22 : human hair, of which there is an unlimited supply. Since its founding in 1998, Matter of Trust has collected donations of human hair and animal fur to 23 the thousands of oil spills that happen each year. The hair and fur are made into mats and brooms and sent to 24 waters to absorb the oil.
Across the United States each day, 300,000 pounds of hair and fur are cut. Matter of Trust is helping organize the collection of this 25 hair and fur through thousands of salons, pet groomers, and ranchers. Individuals can also speak to local hair stylists and pet groomers about sending in leftover hair and fur.