我处要求入口每辆车发卡不超过（）秒/辆次，出口验卡、收款售票不超过（）秒/辆次。

A、8秒；13秒

B、5秒；11秒

C、10秒；12秒

D、6秒；12秒

It has been proved ________ eating vegetables in childhood helps to protect you against serious illnesses in later life. [ ]

A. if  

B. because

C. when  

D. that