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單項選擇題

Although the crankshafts of medium diesel engines appear to be robust, they rely on the support of （） to develop their full strength.

A.the piston rods
B.the crank throws
C.the thrust bearings
D.the main bearings

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單項選擇題

All three systems have the ports （） to swirl the incoming air and direct it in the appropriate path.

A.angled
B.rounded
C.being angled
D.being rounded

單項選擇題

All the rings are slightly rounded on their external top and bottom edges to keep the oil film on the cylinder liner during （） for new piston rings.

A.the running-in period
B.the running process
C.gas exchange process
D.the boiler firing

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