[讨论]OG 32 选项AB的解释不理解？

32. Some buildings that were destroyed and heavily dam­aged in the earthquake last year were constructed in violation of the city's building code.

(A)Some buildings that were destroyed and heavily damaged in the earthquake last year were

(B)Some buildings that were destroyed or heavily damaged in the earthquake last year had been

(C)Some buildings that the earthquake destroyed and heavily damaged last year have been

(D)Last year the earthquake destroyed or heavily
            damaged some buildings that have been

(E)Last year some of the buildings that were
            destroyed or heavily damaged in the earthquake
            had been

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A: In using only one verb tense, were, A fails to indicate that the buildings were constructed before the earthquake occurred.

B: Only B uses verb tenses correctly to indicate that construction of the buildings was completed prior to the earthquake.

大家都讨论过CD和BE的区别了，我想请教大牛AB的区别是什么呢？看起来都是说在地震前完成的建筑啊？谢谢啊！