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

Crankcase dilution is

A.Dilution of fuel in crank case
B.Dilution of lubricating oil in crankcase
C.Dilution of mixture while passing through crankcase in two stroke engines
D.Addition of water in crankcase
E.None of the above