Despite the rising importance and great convenience of the gyrocompass,the magnetic compass still retain its importance because of its（）.

Bales close to the deckhead should be covered to prevent（）.

When the wave period and the apparent rolling period are the same（）.

Where would you find information about the time of high tide at a specific location on a particular day of the year?（）

The company should establish and maintain procedures to control all documents and date which are relevant to（）.