If $c_p$ and $c_v$ denotes the specific heat of nitrogen at constant pressure and constant volume respectively, then

The correct option is B $c_p-c_v=\frac{R}{28}$
$\text{Molar heat capacity}=\text{Molar mass}\times \text{specific heat capacity}$
$\Rightarrow C_P=M{c}_p\&C_V=M{c}_v...\left(i\right)$
$C_P-C_V=R...\left(ii\right)$
From Eq $\left(i\right)\&\left(ii\right)$,
$M{C}_p-M{C}_v=R$
$28C_p-28C_v=R$
$\therefore C_p-C_v=\frac{R}{28}$