In determining if risk of collision exists the following considerations shall be among（）.

单项选择题In a crossing situation on open waters，a sailing vessel shall keep out of the way of all the following vessels EXCEPT a vessel（）.

A.not under command
B.restricted in her ability to maneuver
C.engaged in towing
D.fishing

单项选择题If your vessel is underway in fog and you hear one prolonged and three short blasts，this is a （）.

A.vessel not under command
B.sailing vessel
C.vessel being towed (manned)
D.vessel being towed (unmanned)

单项选择题If there is sufficient sea room，alteration of（）may be the most effective action to avoid close-quarters situation.

A.speed and course
B.speed alone
C.course alone
D.speed or course

单项选择题If there is any doubt as to the proper operation of a radar，which statement is TRUE?（）.

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，（）

A.decrease speed
B.increase speed
C.turn to port for a vessel on her own port side
D.turn to starboard for a vessel on her own port side