GMAT Sentence Correction (SC) | Re: In the mid-1920s the Hawthorne Works of the Western Electric

D has an awkward construction. Actually, D doesn't tell the correct meaning. experiments that investigated changes in conditions'effects on something.

It tells one conditions effect on something while the original sentence means the effect of one change in X to corresponding change in Y.

While B clearly tells that these experiments investigates the effect
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