单项选择题
A.Alert the watch officer that a vessel is approaching the preset CPA limit
B.Warn of small targets that are initially detected closer than the outer guard zone
C.Guard against target loss during critical maneuvering situations
D.Sound an alarm for targets first detected within the 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（）.
单项选择题 The development of（）led to the fully automatic ARPA systems installed on commercial ships.