生态平衡失调的标志是（）和生态平衡失调的功能标志。

The most accurate method of determining gyrocompass error while underway is by（）.

A.Comparing the gyro azimuth of a celestial body with the computed azimuth of the body

B.Comparing the gyro heading with the magnetic compass heading

C.Determining from the chart the course made good between celestial fixes

D.It cannot be determined accurately at sea due to drift of unknown currents