When one of two vessels（）is required to keep out of the way the other must keep her course and speed.
A. In sight of another
B. Sights the another
C. Not in sight of the other
D. In sight of one another
Sludge formation in a diesel engine lube oil system is caused by（）
A. carbonization of oils from the combustion chambers
B. emulsions of lube oil and water
C. coagulation of unburned fuel below the piston rings
D. all of the above
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