JZ-7型空气制动机单独制动阀在全制动位后回运转位时，制动缸压力自300kpA降至35kpA的时间为()。
A. 4s
B. 5s
C. ＜4s
D. ＞4s
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What equipment is used in or near the survival craft？
A. NAVTEX
B. Fathometer
COSPAS-SARSAT
D. EPIRB
Which is not a functional requirement of GMDSS MF/HF equipment？
A. Radiotelephony on 2152 KHz
B. Transmitting distress signals by DSC on 2187.5 KHz
C. Receiving and Watch keeping by DSC on 2187.5 KHz
D. Transmitting and receiving by NBDP with MF
B/FL413/513系列风冷柴油机在怠速600r/min热机时的最小机油压力为（）。
A. 50kP
B. 60kP
C. 100kPa
锅炉汽包常用()材料制作。
A. 普通碳素钢
B. 优质碳素钢
C. 低合金高强度钢
D. 特殊钢
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