In twin-screw engine installations while going ahead，maneuvering qualities are most effective when the tops of the propeller blades both turn（）.

单项选择题In towing，heaving lines are used for（）.

A.passing a tow bridle to the tug
B.passing a messenger line
C.heaving in the tow bridle
D.service lines with rocket line throwers

单项选择题In towing it is desirable for the tug and the vessel to ride wave crests simultaneously because（）.

A.shock loading on the tow line is reduce
B.towing speed is improved
C.the vessel is more visible from the tug
D.the catenary of the tow line is reduced

单项选择题In order to back a right-handed，single-screw vessel in a straight line，you will probably need to use（）.

A.very little rudder
B.some left rudder
C.some right rudder
D.full left rudder

单项选择题In order for a vessel to be engaged in fishing she must be（）.

A.underway
B.using gear which extends more than 50 meters outboard
C.using a seine of some type
D.using gear which restricts her maneuverability

单项选择题In ballasting to survival draft，while in transit，due to extreme wind and wave loads，thrusters or propulsion，if available，should be used to（）.

A.reduce windward mooring tensions
B.maintain vessel heading
C.maximize accelerations
D.increase speed of advance