单项选择题
A red triangular daymark marks（）.
A.the centerline of a navigable channel B.the starboard side of a channel C.a prominent object of navigational interest that has no lateral significance D.area of a channel where passing another vessel is permitted
单项选择题 A power-driven vessel，when towing astern，shall show（）.
单项选择题 A power-driven vessel underway shall keep out of the way of（）.
单项选择题 A power-driven vessel towing another vessel astern (tow less than 200 meters) shall show （）.
