As the piston again reaches BDC, the exhaust valve opens, but the intake valve remains closed. The piston moves upwards on the exhaust stroke to force the burnt gases out of the cylinder through the exhaust port. When the piston reaches TDC, the exhaust stroke is completed and so is the cycle. According to the paragraph, which statement is true? A. Both valves open when the piston reaches TDC on exhaust stroke. B. Both valves close when the piston reaches TDC on exhaust stroke. C. The exhaust valve open when exhaust stroke begins.