A light used to signal passing intentions must be an（）.

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

单项选择题A traffic separation zone is that part of a traffic separation scheme which（）.

A.is between the scheme and the nearest land
B.contains all the traffic moving in one direction
C.is designated as an anchorage area
D.separates traffic proceeding in one direction from traffic proceeding in the opposite direction

单项选择题A vessel using a traffic separation scheme shall（）.

A.only anchor in the separation zone
B.cross a traffic lane at as small an angle as possible
C.avoid anchoring in areas near the termination of the scheme
D.utilize the separation zone for navigating through the scheme if she is impeding other traffic due to her slower speed