电火花检漏仪的探头分为弹簧式和（）两种。
A、铝刷式
B、膜盒式
C、铜刷式
D、真空式
参考答案：C
They must have been enjoying themselves there,otherwise they _________ so long.
A．can’t have stayed
B．wouldn’t have stayed
C．needn’t have stayed
D．couldn’t stay
积聚于“膻中”的气是
A．精气
B．元气
C．宗气
D．卫气
E．营气
