— 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

柱钢筋绑扎的施工工艺流程为：调整插筋位置，套入箍筋→立柱子四个角的主筋→立柱内其余主筋→绑扎钢筋接头→将主骨架钢筋绑扎成形。