航海英語遇險(xiǎn)通信單項(xiàng)選擇題每日一練(2019.01.25)

來源：考試資料網(wǎng)

1 When can routine communications be resumed on a frequency or channel on which radio silence has been imposed? （）

2 What is the fundamental purpose for imposing radio silence? （）

3 If your vessel is underway in fog and you hear one prolonged and three short blasts，this indicates a（）.

4 At night，if you see a vessel ahead displaying the lights shown you should（）.

5 The service life of distress signals must be not more than（）.