（） is usually driven by the engine camshaft and supplies pilot air to the cylinder air start valve.

（） is made of a boss with separated blades mounted into it.

A.A variable pitch propeller
B.A variable pitch nut
C.A fixed pitch parallel
D.A fixed pitch screw

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（） is fully floating in both connecting rod small end and the piston skirt.

A.The piston rod
B.The cross head pin
C.The gudgeon pin
D.The crank-pin

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