why should the SES operators be very careful when the ship enters the area where three ocean regions overlap? Because（）. ["the weather over there is always terrible","the condition there is complicated","the signals are too strong","their SES may receive the signals from unwanted satellite"]
什么是体积分数、质量分数？两者的关系如何？
The quality of EGC messages is（）affected by the position of the ship, the time of reception and climatic conditions. ["sometimes","all times","never","partly"]
采用打桩法人工地基时，应注意局部换土的新土应与周围土质接近，为什么？
The identification character of each Navtex station is regarded as（）to the messages. ["the only preamble","a part of the preamble","the closing","the suspensio"]
门诊日志的主要内容有哪些？
