单项选择题
The closest point of approach (CPA) of a contact on a relative motion radar may be determined（）.
A.immediately when the contact is noted on radar B.only if the radar scope is watched constantly C.after the contact has been marked at least twice D.by an occasional glance at the radar
单项选择题 The articulated light is superior to other types of buoys because（）.
单项选择题 The ARPA may swap targets when automatically tracking if two targets（）.
单项选择题 The 3-cm radar as compared to a 10-cm radar with similar specifications will（）.
