单项选择题
A.the central cooling system, different
B.the central cooling system, the same
C.the open cooling system, different
D.the open cooling system, the same
单项选择题 （）is harmful for fuel pumps, fuel valves, cylinder liner, exhaust valve seats, and the turbocharger blades as well.
单项选择题 The booster pump, which supplies diesel oil to（） , should have a possibility of being powered by compressed air or by emergency power.
单项选择题 A full-flow 50μm filter is installed ,（） so the injection system components on the main engine are safeguarded.