Sentence Correction

Some building 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

The ans is B. What I have learnt from the perfect tenses is that they are used to indicate the action that had been completed before another started.(as u can see in the underlined part).

So, Doesn't B indicate that the construction of the buildings had been completed before the earthquake occurred.

Please clarify...my knowledge of the tenses has completely been reversed in this case.

Hi,
You understood it correctly. He is talking about the buildings that were destroyed last year because of earthquake. In that context(aftermath) he says, those buildings were actually built violating the city building codes.

--------------------------------|----------------------|-------------------
Buildings were constructed ------- Earth quake-----------Reporting now
(Before past action) --------------(Past action)
(Before Last year) -----------------(Last year)