A vessel continually lists to one side and has a normal rolling period. Which statement is TRUE?（）.

单项选择题A vessel constrained by her draught may，in addition to the lights prescribed for power-driven vessels in Rule 23，exhibit where they can best be seen（）or a cylinder.

A.two all-round red lights in a vertical line
B.three all-round red lights in a vertical line
C.two all-round yellow lights in a vertical line
D.three all-round green lights in a vertical line

单项选择题A vessel conducting mine clearing operations will show（）.

A.three balls in a vertical line
B.two balls in a vertical line
C.one ball near the foremast and one ball at each fore yard
D.one diamond near the foremast head and one ball at each fore yard

单项选择题A vessel being towed will show（）.

A.a forward masthead light
B.sidelights and a sternlight
C.a towing light
D.All of the above

单项选择题A vessel being towed astern shall show at night（）.

A.the lights required for a power-driven vessel underway
B.only the required masthead lights
C.a sternlight only
D.sidelights and a sternlight

单项选择题A vessel being pushed ahead is required to carry which of the following lights?（）.

A.Sidelights and a stern light
B.Sidelights only
C.Sidelights and a small white light at each end
D.A small white light at each end