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.

A.by an fuel valve
B.through an inlet valve
C.with an exhaust valve
D.from an outlet valve

A.piston crown
B.piston ring groove
C.piston skirt
D.piston ring area

A.one propulsion
B.two propulsions
C.two revolutions
D.one revolution