Choose the sentence which has the closest meaning to the original one.
Those who are riding a motorbike are not allowed to take off their helmet.
A.Those who are wearing a helmet are not allowed to ride a motorbike.
B.It is the helmet that one needn't wear when he is riding a motorbike
C.You should not wear a helmet when you are riding a motorbike.
D.People must never take their helmet off while they are riding a motorbike.