－It’s necessary to limit the speed of electric bikes.

－Yes, most riders of electric bikes in China        40-50 kilometers per hour often ignore red lights,        the risk of traffic accidents.

A．reaching; increase

B．reach; increase

C．to reach; to increase

D．reaching; increasing

公路隧道控制坡度的主要因素为（）。

A.排水问题

B.通风问题

C.通行问题

D.动力问题