When forward motion is imparted to it from an external source, air is forced.

当由外部能源强迫其向前运动时，空气被迫进入进气道。

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Always use an external source of nitrogen or air for this purpose.

做类似事情时，只能用氮气或空气作为外在气源。

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Always use an external source of nitrogen or air for this purpose.

做类似事情时，只能用氮气或空气作为外在气源。

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