下列哪项因素与患病率的变化无关（）

A.发病率的升高或下降

B.病死率的升高或下降

C.人口总数自然增加或减少

D.治疗水平的提高或降低

E.存活时间长短

All the following statements about cost baseline are correct EXCEPT: （）.

A．It is a time phased budge

B．To measure disbursements, a spending plan can be used as a cost-baselin

C．It is used to measure and monitor project performanc

D．All projects have one cost baselin