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單項選擇題

Pistons may be made in （） in order to keep the weight down for balancing purposes at high speed.

A.cast iron
B.forged steel
C.stainless steel
D.aluminum alloy

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單項選擇題

Piston No2 of main engine has been removed, and it will be （） by noon tomorrow.

A.lifted
B.reassembled
C.dismounted
D.disassembled

單項選擇題

Persistent knocking in one cylinder of a diesel engine could be caused by（）.

A.a low load on that cylinder
B.sluggish piston ring action
C.excessive piston crown cooling
D.excessive clearance of piston pin

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