单项选择题
Simplex tailshaft seal equipment’s working condition is terribleThe main cause is （）
A.the shafting’s vertical vibration B.violent friction and sea water corrosive C.friction and high temperature D.violent friction and high temperature
单项选择题 The center line condition of the transmission shaft can be checked by（）
单项选择题 In the navigation（） cause the shafting over load easily.
单项选择题 When the vessel on the full speed ahead, if full astern immediately （） the main engine start astern and fuel injection.
