A vessel sounds one short blast. This signal indicates the vessel（）.

单项选择题A vessel not under command sounds the same fog signal as a vessel（）.

A.towing
B.constrained by her draft
C.under sail
D.All of the above

单项选择题A vessel displaying three red lights in a vertical line is（）.

A.not under command
B.aground
C.dredging
D.constrained by her draft

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