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單項(xiàng)選擇題

The pitch ratio of a propeller is the mean pitch divided by （）.

A.the propeller diameter
B.the propeller radius
C.the pitch angle
D.the length of helix

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單項(xiàng)選擇題

If a line at right angles to the axis rotates about that axis and, at the same time, moves parallel to the axis, it will generate （）.

A.a helix
B.a helicoidal
C.a curve
D.a cone

單項(xiàng)選擇題

When a point rotates about an axis and, at the same time, moves parallel to that axis, it describes （）.

A.a line
B.a circle
C.a helix
D.an epllicate

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