The correct option is B

In petrol engines and for stroke engines the suction consists mixtures of both air and fuel. Suction is also known as intake or induction. Stroke of the engine begins at top dead center (T.D.C) and ends at bottom dead center (B.D.C). The suction valve must be in open position while the piston pulls mixture of air and fuel into the cylinder by producing vacuum pressure into the cylinder through its downward motion. This is the first stroke in four stroke engines.