Riders who wear bicycle helmets can greatly reduce the risk of significant injury. Therefore, doctors working in an emergency room can expect that, out of cyclists admitted to hospitals, those wearing bicycle helmets will have injuries that are less severe than will those not wearing a helmet.

Which of the following is necessary to evaluate the argument?

A:The probability that those cyclists admitted to an emergency room have suffered similar accidents in the past

B:The durability of bicycle helmets over the course of many years

C:The number of riders wearing bicycle helmets compared to the number not wearing helmets

D:Whether the bicycling activities of cyclists using a helmet differs from the activities of those not wearing a helmet

E:The number of medical staff who are in the emergency room when an injured cyclist arrives