The valve face must seat evenly against the valve seat in the cylinder head to prevent leaks from the cylinder during the compression and power strokes.
【简答题】听对话选择图片:你将听到五段小对话,每段对话你将看到三幅供选择的图片。请你根据听到的对话 内容,选择相应的图片。每段对话之后你有5秒钟的答题时间。听一遍。 ( )1. A. B. C. ( )2. A. B. C. ( )3. A. B. C. ( )4. A. B. C. ( )5. A. B. C.