--Is Bob still performing ?

--I’m afraid not . He is said       the stage already as he has become an official.

A．to have left

B．to leave

C．to have been left

D．to be left

从产品装配出发，每道工序和每个车间按需要向前一道工序和车间发出工作指令，前一道工序和车间按这些指令进行生产，这种方式称为______

A．准时生产
B．精益生产
C．推动式方法
D．拉动式方法