GMAT Sentence Correction (SC) | Re: Active underwater faults are observed carefully, tectono

i got the correct answer in 1:11 minutes.

first round of elimination : 2 independent clauses. so we need semi-colon, A and B out.
2nd round of elimination : active voice is preferred and parallelism is required when it comes to active voice. hence E and C are eliminated.

D is a clear winner.

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