Our courses are created by other users and therefore the answers are subject to the opinion of the course creator. It is also possible that users may make mistakes during course creation. If your answer is correct, click 'I was right'. From then on, the answer will be accepted (note that it will also become the primary answer in multiple-choice and other modes).
If you feel an answer is incorrect, you should use the Report Mistake function. The course owner will see this if they go into their course analysis functions in their create course screen. But, if the course owner is not active, it is unlikely that they will take any action.
Memory offers no guarantee of the quality of courses created by other users.