单项选择题
A.Only a radar expert can determine if the radar is operating
B.All radars have indicator lights and alarms to signal improper operation
C.A radar range compared to the actual range of a known object can be used to check the operation of the radar
D.The radar resolution detector must be energized to check the radar
单项选择题 If it becomes necessary for a stand-on vessel to take action to avoid collision，she shall NOT，if possible，（）
单项选择题 Any vessel（）any other shall keep out of the way of the vessel（）.
单项选择题 Any alteration of course and／or speed to avoid collision shall，if the circumstances of the case admit，（）to another vessel observing visually or by radar.