The schedule control process for a project ______ .

A．focuses on starting the project earlier than scheduled

B．is necessary for controlling changes to the project schedule

C．is concerned only with activities that are on the critical path

D．should focus entirely on activities that are difficult to carry out

拉姆塞价格是一种次优价格，但拉姆塞定价法也存在以下缺点（）。

A.对需求弹性等信息的获得较困难，从而不能完全按照拉姆塞定价法来定价

B.根据需求弹性的大小在不同产品间分摊福利损失，很难公允

C.不能保证企业收支平衡

D.不能确保企业固定成本的补偿