单项选择题
Which vessel，when anchored at night，is NOT required to show anchor lights?（）.
A.A power-driven vessel B.A vessel engaged on pilotage duty C.A vessel dredging D.A vessel restricted in her ability to maneuver
单项选择题 While underway，in fog，you hear a whistle signal of one prolonged blast followed by two short blasts. This signal is sounded by a vessel（）.
