物流系统一般由输送系统。储存系统和操作系统组成。
参考答案：对
如图所示的光路图中，正确的是
A．
B．
C．
D．
.--- Is your sister a factory worker or a doctor?
--- ________________.
A．Yes, she is
B．No, she isn’t
C．A factory worker
D．Yes, she is a doctor
