单项选择题
A.Pulse width
B.Pulse repetition frequency
C.Peak power
D.Target brightness
单项选择题 Which of the following statements is TRUE regarding crane operations（）.
单项选择题 Which of the following statements is TRUE regarding automatic identification systems（AIS）（）.
单项选择题 When your vessel is proceeding to the area of traffic density，（）is used to determine the exact ranges of other ships or objects in the vicinity.