题目选项分析

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?

【选项】Whether the bicycling activities of cyclists using a helmet differs from the activities of those not wearing a helmet