K-CHIEF500/DC C20的分布式处理系统不包含（）。
A.CAN总线
B.以太网
C.RS485总线
D.输入/输出模块
参考答案：B
----_______did you go last Saturday ? ---- I went to the zoo
A．How
B．When
C．Where
D．Why
_____ UN report says in 1990 _____ number was over five billion. [ ]
A. The; a
B. An; the
C. A; the
D. A; a
