GMAT Sentence Correction (SC) | Re: The professor assumed that Michelle probably have stayed up late last

I rejected the choice C as it changes the meaning of the original sentence. Original choice shows the possibility while choice C shows the certainty. To me, no choice seemed to be correct. so, I end up selecting A; however, I knew that there should be past perfect instead of present perfect in choice A.

Please advise how to select one choice between two when both seems to be incorrect.

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