电场中有一点P，下列说法正确的是[ ]

A．若放在P点试探电荷的电量减半，则的场强减半

B．若P点没有试探电荷，则P点场强为零

C．P点场强越大，则同一电荷在P点所受电场力越大

D．P点场强方向为试探电荷在该点的受力方向　

Schedule control is concerned with all the followings except （）.

A.influencing the factors that create schedule changes to ensure that the changes are beneficial

B.determining that the schedule has changed

C.managing the actual changes when and as they occur

D.changing the schedule based on customer demands