# If $C_P$ and $C_V$ denote the specific heats of nitrgen per unit mass at constant pressure and constant volume respectively, then :
( A ) $C_P - C_V = 28R$
( B ) $C_P - C_V = R/14$
( C ) $C_P - C_V = R$
( D ) $C_P - C_V = R/28$