In-place edits are very limited because the question is already present on some exams. For example, two people already chose the answer that you’re trying to delete.
When adding or removing answers, you must create a new version of the question. It is also strongly recommended that you create a new version of a question if making edits that would change the meaning of the question or any answer, as users may already be taking an exam based on the original wording, and will be surprised if the meaning of an answer changes after they have selected it.