Source is GMATprep and I wonder if we can have such flaws in GMATprep questions
VERY unlikely. As Kevin says, just id the question type, and follow the instructions. There is NO ambiguity in the interpretation of the stimulus or the answer choices. (On the GMAT, especially in the verbal section, removing ambiguity is by far the most importan design issue that the test-maker faces.)
The only reason I thought it may have been bad is because the correct answer-the resolver-is unlikely. That actually doesn't make it a flawed question though. All GMAT questions are vetted and then administered as experimental questions. If a certain expected fraction select the accredited response (accounting for difficulty level), then the question stands. Because this is an official GMAT question, it must be the case that not too many people were bothered by the fact that the resolver was unlikely (indeed, it is possible that not too many people even noticed or thought about that).
Kaplan Teacher in Toronto