单项选择题
If the beacon is mounted at a wrong place, it may（）by sea water, chemicals, exhaust and vibrations.
A.be damaged B.work normally regardless of harmful conditions C.not wok though it is not in a bad condition
单项选择题 By using（）system a ship can send a distress message and know with certainty it will be received.
单项选择题 For COSPAS-SARSAT system,（）usually transmit initial COSPAS-SARSAT alert.
单项选择题 COSPAS-SARSAT is intended to be used for（）.
