西部地区基础设施和基础产业的发展应是( )的。
A．渐进式
B．常规式
C．跨越式
D．跳跃式
参考答案：C
Many things _____ impossible in the past are quite common nowadays.
A．having considered
B．considered
C．to be considered
D．considering
近似数2.55×106精确到（ ）位，有效数字是（ ）．
