20.The volumes above the piston at the extremities of its travel are the clearance volume at topdead center position, and the cylinder volume at bottom dead center position. The ratio of cylinder volume to clearance volume is the nominal compression ratio. When the clearance volume and cylinder volume are 2 m3 and 8 m3 respectively, the compression ratio is .
(A)0.25
(B)16
(C) 4
(D)10