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單項(xiàng)選擇題

（） 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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單項(xiàng)選擇題

（） of an engine crankshaft can be detected by measuring deflections of crank webs for each unit of the engine.

A.Misalignment
B.Length
C.Strength
D.Stresses

單項(xiàng)選擇題

（） may be the first possible cause which makes the engine to lose power or slow down when it is running.

A.Hot bearing
B.Starting valves
C.Unequal distribution of load
D.Excessive crankshaft clearance