单项选择题
Some radio waves（）the surface of the earth because of its（）.
A.are capable of following / distance B.can follow / altitude C.can hardly follow / shape D.are unable following / angle
单项选择题 Ships equipped with Inmarsat SES send distress alerts both（）.
单项选择题 In addition to communication equipment, the GMDSS will introduce requirements of SARTs and EPIRBs designed to improve the（）.
单项选择题 The GMDSS must combine all various subsystems, because（）.
