Those who are riding a motorbike are not allowed t...

Câu hỏi: 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.