No captcha question on quiz

I have one quiz with 9 questions, 2 possible answers each. I checked the box next to “Require question based captcha to submit the quiz.” There is a field at the bottom of the quiz but there is no label attached to it, just a blank field. I feel certain that the field is where the answer to the captcha question should be entered but there is no question to answer. Additionally, if I complete the quiz and the “captcha” field is empty, the submit button still works. How do I get this fixed?