I had a few CS professors at the University of Illinois that allowed students to answer “I don’t know” for any question and receive 25% of the points on that qu

I had a few CS professors at the University of Illinois that allowed students to answer “I don’t know” for any question and receive 25% of the points on that question. (I utilized this multiple times myself) If this professor did that, would people be less angry about him putting an unanswerable question on the exam?