空气压缩机必须有（）保护装置。
A、压力表
B、电流表
C、电压表
D、安全阀
参考答案：A, D
Many policemen and soldiers are ______ the forest _____ the prisoner escaping from prison.
A．searching for; searching
B．searching; searching
C．searching; in search of
D．in search for; searching for
触觉语音震颤增强主要见于
A．气胸B．胸腔积液C．大叶性肺炎D．胸膜肥厚粘连E．肺气肿
