单项选择题
Navigation lights must be displayed in all weathers from sunset to sunrise. They also（）.
A.must be displayed when day signals are being used B.must be displayed when moored to a pier C.may be extinguished at night on open waters when no other vessels are in the area D.may be displayed during daylight
单项选择题 Lighted information markers show（）.
单项选择题 If your vessel were proceeding down river (descending)，a green square marker with a green reflector border on the right bank would be a（）.
单项选择题 Environmental loading consists of the forces caused by wind，waves，and（）.
