The first quiz in the inbound marketing course course is broken as it is marketing all posible answers as incorrect. The quest is titled ''What is inound marketing ?''
Just to confirm - are you referring to this question here?
If so, is this error still occuring for you? I was able to test out and submit an answer that was marked as correct. If it's not working for you, can you provide a screenshot of the error message you're seeing when trying to select the answer? You may need to clear your cache/cookies from all time to reset the browser. Please note that the quizzes are also optional, so you don't need to wait on taking the rest of the course.