突出矿井应在井下设置压风自救系统，长距离的掘进巷道中，应每隔（）米设置一组压风自救装置。
A、100
B、70
C、50
参考答案：C
A．HCl
B．NaCl
C．Na2O
D．NaOH
Would you mind ________ the noise here? The baby is sleeping.
A．not to making
B．not to make
C．not making
D．to not make
