A.not under commandB.agroundC.dredgingD.constrained by ……

单项选择题A vessel constrained by her draft may display（）.

A.three all-round red lights instead of the lights required for a power-driven vessel of her class
B.the same lights as a vessel restricted in her ability to maneuver
C.three all-round red lights in addition to the lights required for a power-driven vessel of her class
D.the lights for a power-driven vessel which is not under command

单项选择题A vessel constrained by her draft may display（）.

A.three all-round red lights
B.two 225°red lights
C.three all-round blue lights
D.two 225°blue lights

单项选择题A towing light is（）.

A.shown below the sternlight
B.white in color
C.displayed at the masthead
D.a yellow light having the same characteristics as the stern light

单项选择题A towing light is（）.

A.shown at the bow
B.white in color
C.shown in addition to the sternlight
D.an all-round light

单项选择题A towing light（）.

A.flashes at regular intervals of 50-70 flashes per minute
B.is yellow in color
C.shows an unbroken light over an arc of the horizon of not less than 180°nor more than 225°
D.All of the above