22. 船舶展示一橙色帆布，其上佈置一黑色方形與一黑色圓形標誌或其他適合標誌之信號，代表何種意義？ (A)我需要拖船 (B)我需要引水 (C) 我需要清運廢棄物 (D) 對空求救信號

17. Your vessel was vibrated heavily at a range of numbers of revolutions of the engines because synchronization occurs between the periods of a vibration of the hull and those caused by the inertia of the reciprocating parts of engines. What do we call this speed? (A)Regulative speed. (B)Critical speed. (C)Calibrating speed. (D)Difficult speed.