Four- stroke engine

The four - stroke engine works by heating fuel and air in a ____________________ . During the first stroke , the ____________________ valve lets fuel and air into the cylinder . Then the valve closes during the ____________________ stroke . A piston moves up to condense the air and ____________________ . Then the mixture ____________________ during the power stroke . The final stroke ____________________ gas . This is the ____________________ stroke .
Source : Jim D . Dearholt " Career Paths Mechanics " Express Publishing 201 2