我国自然资源的最基本特征是[ ]
A．资源丰富，取之不尽，用之不竭
B．总量丰富，人均不足
C．总量贫乏，人均不足
D．总量丰富，人均量多
答案：B
_____ is known to us all is that the 2008 Olympic Games will take place in Beijing. [ ]
A. It
B. What
C. As
D. Which
GGH吹扫装置的行程编码器为什么要选择双通道发送？
