It is shown that men have         as women do on average while driving according to recent statistics.

A．twice as many serious accidents

B．serious accidents as twice many

C．twice serious accidents as many

D．serious accidents as many twice

凸轮式刮板流量计的（）在转子园筒壁上的槽内滑动，能伸出也能缩回

A、滚柱

B、凸轮

C、连杆

D、刮板