单项选择题

A power-driven vessel towing another vessel astern (tow less than 200 meters) shall show ().

A.three masthead lights in a vertical line instead of either the forward or after masthead light
B.two masthead lights in a vertical line instead of either the forward or after masthead lights
C.two towing lights in a vertical line at the stern
D.a small white light aft of the funnel