A.two all-round red lights in a vertical lineB.two yell……

单项选择题A power-driven vessel leaving a quay or wharf must sound what signal? （）

A.Three short blasts
B.A long blast
C.A prolonged blast
D.No signal is required

单项选择题A light used to signal passing intentions must be an（）.

A.alternating red and yellow light
B.alternating white and yellow light
C.all-round white or yellow light
D.all-round white light only

单项选择题A fishing vessel is approaching a vessel not under command. Which statement is TRUE? （）

A.The fishing vessel must keep clear of the vessel not under command
B.If the vessel not under command is a power-driven vessel，she must keep clear of the fishing vessel
C.They must exchange whistle signals
D.Both vessels are required to take action to stay clear of each other

单项选择题A facility used for the discharge of a cargo of a particular hazard，such as chlorine，butane or ethane，must have what to warn water traffic of an immediate danger during fire or cargo release?（）

A.An emergency boat and crew
B.A siren or rotating flashing light
C.Flashing red lights located one-half mile upstream and downstream of the facility
D.Buoys with flashing lights controlled from shore，located one-half mile upstream anddownstream of the facility

单项选择题A 20-meter power-driven vessel pushing ahead or towing alongside will display（）.

A.a single white light forward
B.two masthead lights in a vertical line
C.two towing lights in a vertical line
D.two all-round red lights where they can best be seen