Three years ago in Beijing my best friend David was hit by a car while riding a bike

问题补充：

Three years ago in Beijing, my best friend, David, was hit by a car while riding a bike, a terrible brain injury.

A. caused

B. to cause

C. causing

D. being caused

答案：

A. caused

B. to cause

(答案→)C. causing

D. being caused

解析：考查非谓语动词作结果状语。Doing作结果状语，表示自然而然的结果；to do表示出乎意料的结果。因为被车撞，所以受了很严重的伤，是车祸造成的自然而然的结果，所以选C。