28._____it was once a heavily-polluted rice field, it is now much cleaner.
(A) Because
(B) Whenever
(C) However
(D) Although
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統計: A(219), B(224), C(160), D(2067), E(0) #728136
統計: A(219), B(224), C(160), D(2067), E(0) #728136