In complying with the Rules，of what must the mariner take due regard?（）.

单项选择题In dense fog a vessel without operational radar may not be justified（）at all but should anchor if it is safe and practicable for her to do so.

A.to be underway
B.on under way condition
C.to stop engine
D.in being under way

单项选择题In determining a safe speed（）shall not be among those taken into account.

A.the state of visibility
B.the power of the vessel
C.the traffic density
D.the maneuverability of the vessel

单项选择题In determining a safe speed（）shall not be among those taken into account.

A.the presence of the background light at night
B.the state of wind，sea and current
C.the number of crew on board
D.the draught in relation to the available depth of water

单项选择题In determining a safe speed（）shall not be among those taken into account.

A.the characteristics，efficiency and limitation of the radar equipment
B.any constraints imposed by the radar range scale in use
C.the effect on radar detection of the sea state，weather and other sources of interference
D.the safe working load of the cranes both on board and ashore

单项选择题In determining if risk of collision exists，if there is any doubt，such risk shall be deemed to（）.

A.exist
B.exists
C.existing
D.to be existed