Biopak240正压氧气呼吸器校验仪的构造主要有（）等构成。
A.流量计
B.排气阀锁
C.舌片
D.气球
参考答案：A, B, C, D
The old man needs at most five hours' sleep a night, but he _______ for over seven hours tonight. [ ]
A. has gone to bed
B. has slept
C. has gone to sleep
D. has fallen asleep
最可能的原因是
A．脑梗塞
B．脑出血
C．心脏骤停
D．脑血栓
E．高血压脑病
