If he fails to have enough concentration , he might produce an effect different from the desired one which can be potentially dangerous . The sole exception to this energy restriction are his wings which he can call forth at will without much problem . He is n't quite sure how they work , but extensive use is very taxing to his body .

Question: What may be the reason for not being sure how the wings work ?
Answer: The wings are new .They did n't know they had them for a long time .They were told they did n't have wings .None of the above choices .