单项选择题
Despite the rising importance and great convenience of the gyrocompass,the magnetic compass still retain its importance because of its（）.
A.great convenience B.finding true north C.magnetic characteristics D.simplicity and reliability
单项选择题 Which of the following is not an operation mode of AIS?（）
单项选择题 （）is where the crew eat their meals.
单项选择题 When the wave period and the apparent rolling period are the same（）.
