GMAT Sentence Correction (SC) | Re: Scientists at the Los Alamos National Laboratory have

+1 for D.
This is a classic parallelism problem, touching upon simple vs complex gerunds. Simple gerunds such as "verb-ing" should never be parallel to complex gerunds such as "the/a/an+ verb-ing + of the..". Once you know this, B starts to look awkward and unparallel.

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