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單項(xiàng)選擇題

The film of oil between the rings and the liner is not only essential for the lubrication but also （） achieving a gas seal.

A.play a great part on
B.run a role in
C.plays an important part in
D.acts as important part at

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單項(xiàng)選擇題

The film of oil between the rings and the liner is not only essential for the lubrication but also plays an important part in achieving （）.

A.an oil seal
B.removing heat
C.a gas seal
D.cooling the piston

單項(xiàng)選擇題

The figure that the volume of air at BDC is divided by the volume of air at TDC is termed as（）.

A.ignition ratio
B.power ratio
C.compression ratio
D.injection ratio

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