First, selecting security questions as the only authentication method is less secure. Second, since you modified a question, ...

First, selecting security questions as the only authentication method is less secure.  Second, since you modified a question, note that this will not invalidate any previous answers to that question, so make sure those answers will still make sense.  Finally, since you deleted a question, note that this will invalidate any previous answers to that question and may require users to re-register as a result. Do you want to proceed?