31. 船舶推進軸系統中，就下圖而言(7)應為下列何者？ (A) 前軸承 (B) 後軸承 (C) 前軸封 (D) 後軸封

10. The followings are procedures of start the engine. Which step is incorrect? (A) Open the starting air reservoir valve and safety valve. (B) Hold the START switch pressing for 2 to 3 seconds, and make sure of ignition. Only then release the switch. (C) Close the starting air reservoir valve. (D) Keep the control air valve opened during a run.