急性小脑幕上硬膜外血肿，最常见的出血来源是

A．脑膜中静脉
B．脑膜中动脉
C．静脉窦
D．骨折的板障静脉
E．脑表面桥静脉

A combustible gas indicator meter is calibrated to read the percentage of（）.

A.vapor to oxygen

B.the flammable limit concentration

C.the autoignition concentration

D.the lower explosive limit concentretion