单项选择题
A.the range of antenna can cover everywhere in the world
B.we can know the ship’s exact position
C.that the distress alert can be located as soon as possible
D.antenna of permanent earth stations may be directed towards fixed points in the sky
单项选择题 The frequency（）the safety message will be transmitted shall be included in DSC safety call.
单项选择题 We consider（）send a helicopter with medical facilities to the distress area.
单项选择题 Radiotelephony communication or radio telex communication or both will be carried out by terrestrial or satellite means,（）the equipment fitted on ship and the area in which the incident occurs.