An aneroid barometer on a boat should always be（）.

单项选择题An anchored vessel is servicing an aid to navigation and is restricted in her ability to maneuver. Which lights will she show? （）

A.Three lights in a vertical line，the highest and lowest red and the middle white，and anchor lights
B.Three lights in a vertical line，the highest and lowest red and the middle white，ONLY
C.Anchor lights ONLY
D.Anchor lights and sidelights ONLY

单项选择题An all-round flashing yellow light may be exhibited by a(n)（）.

A.vessel laying cable
B.vessel towing a submerged object
C.vessel not under command
D.air cushion vessel

单项选择题An airplane should NOT send which signal in reply to a surface craft?（）

A.Opening and closing the throttle
B.Rocking the wings
C.Flashing the navigational lights off and on
D.Flashing Morse T

单项选择题An advantage of using chain lashing on heavy vehicles aboard Ro-Ro vessels is that it（）.

A.has long life
B.is light weight
C.absorbs shock
D.has fine adjustment

单项选择题An advantage of the Christmas Tree towing method is to（）.

A.increase the towing hawser's catenary and provide more spring
B.reduce catenary，allow operation in shallower water，and to release one barge without breaking up the entire tow
C.enable one tug and its crew without any outside assistance to make up or break down the tow
D.provide rapid delivery of logs from the northwestern United States to Hawaiian sawmills