（） should not undertake any task which will interfere with the supervision duties relating to the main machinery and associated equipment.

（） pistons have low inertia and high coefficient of thermal expansion.

A.Cast iron
B.Cast steel
C.Forged steel
D.Aluminum

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（） of the A-frames there is a strong cast iron frame called the scavenging air box.

A.At the top
B.At the bottom
C.In the top
D.In the bottom

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