The correct sentence is C. Will I be seeing Dr. Ross or Dr. Winters?.
Dr. is the correct abbreviation of doctor, while "Doc." (option B) is not the correct form to shorten the word doctor. Moreover, in options A and D, the sentences contain the abbreviation MD which comes from Latin (Medicinae Doctor). MD is a short form to refer to Doctor of Medicine, so in those two options, the term doctor would be unnecessarily repeated. Besides, in option D, the abbreviation "Doct." for doctor is not appropriate.