As that question is written, you are correct that the best answer is D. No answer is "correct", but the answer you chose is the best. I get what they were trying to ask and feel with a little editing, that could be a very good question and one that is in the style of the AAMC test writers. But the combination of CrO3 and H2SO4 must include H20, which over time would remove the protecting group from the alcohol and expose it to oxidative conditions. Even if they would have chosen PCC (CrO3, HCl, and pyridine with no water present), the aldehyde would not have been oxidized under those conditions, and no answer would have been right.
Excellent work recognizing that error. I'm not sure what the source of that question is, but the style of the question is very good and thankfully you have a strong working knowledge of organic chemistry to catch any of the minor errors they make on other questions.