Question

The river has become much ______ than before because of the waste water from the factories.
A. dirty    B. dirtier  C. Dirtiest

Answer 1

B

解析試題分析：句意：由于來自工廠的廢水，這條河變得比以前更臟了。句中暗含現(xiàn)在的河與以前的河相比較，所以應(yīng)用比較級。故選B。
考點：考查介詞短語。