13. 在日間時，救生站或海上搜救單位對遇險船舶或人員，發出將儘速前往援助信號，包括聲音與光線（雷電閃光）3個，其發射間隔為幾分鐘？ (A)1/2 (B)1 (C) 2 (D) 3

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.