单项选择题
A.Off center
B.True motion
C.Stabilized
D.Head up
单项选择题 Your ARPA has two guard zones.What is the purpose of the inner guard zone（）.
单项选择题 Your ARPA has automatic speed inputs from the log．Due to currents，the log is indicating a faster speed than the speed over the ground.What should you expect under these circumstances（）.
单项选择题 Your ARPA has been tracking a target and has generated the targets course and speed.The radar did not receive a target echo on its last two scans due to the weather.What should you expect under these circumstances（）.