下列关于胶体的说法中正确的是[ ]

A、胶粒能对光产生散射现象

B、胶粒不能通过滤纸

C、胶体外观不均匀 　　

D、胶体不稳定，静置后容易产生沉淀

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