Q. Which one of the following is a correct statement

• (A) the exhaust valve of a four stoke I.C. engine should open exactly at the end of expansion stroke
• (B) in actual practice, inlet valve of a four stroke I.C. engine should open exactly at the start of suction stroke
• (C) the inlet valve remains open approximately for 180?
• (D) valve overlap is the angle during which both the inlet and exhaust valves remain open simultaneously