--- Julia, what were you doing when Anna called you?

--- I ________ my housework and was starting to take a bath.

A．had finished

B．have finished

C．were finishing

D．will finish

对于确定情况下的固定订货量库存模式而言，所谓确定情况是指（）

A、需求均匀

B、各种成本数据固定

C、订货提前期确定

D、交货提前期为零

E、无缺货

F、有数量折扣