Official Explanation Magoosh :
Version (A) is clumsy and wordy. We get the idea of Washington's choices, but this is a poor colloquial construction that has, at best, a tenuous connection to the rest of the sentence. This is incorrect.
Version (B) is grammatically correct, but it greatly obscures the meaning of the sentence. "Might have..." implies that we do not know how Washington actually conducted the war. It does imply that the war could not have been won irrespective of Washington's
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