—Can you describe it happened?
—Yes, I was riding on my bike a car knocked me down from behind.
A. when; as
B. how; as
C. how; when
D. how; while
网友回答
A. when; as
B. how; as
(答案→)C. how; when
D. how; while
解析：句意：你能描述一下它是怎么发生的吗？好的，我正在骑自行车时，突然一辆车从背后把我撞倒了。when突然 。故选C