单项选择题 Increased air （） will raise scavenge efficiency and allow a greater mass of air to be compressed； more fuel may now be burned giving an increased power.

单项选择题 In the suction stroke air is induced into the cylinder （）In the compression stroke the air is compressed.

单项选择题 In the sentence “In some designs the cylinder oil is timed so that the oil injects only on the piston ring belt, the "piston ring belt" means （）.