采区内、采区之间和各水平之间的风量调节称为（）。
A、矿井风量调节
B、局部风量调节
C、统一通风
D、分区通风
参考答案：B
Microsoft ended support for Windows XP after April 8, which _______a major operating system for some Chinese computer users, and advised users to upgrade to Windows 8.1.
A．remained
B．remains
C．is remaining
D．is remained
下列物质中不属于苯菲尔溶液的组成成分是（）
A、K2CO3
B、二乙醇胺
C、KHCO3
D、V2O5
