(d) Electric displacement vector $\overrightarrow{D} = \varepsilon\overrightarrow{E}$
But $\varepsilon = K\varepsilon_{0}$
Where, $K =$ dielectric constant and $\varepsilon_{0} =$ permittivity of free space
$\therefore\overrightarrow{D} = K\varepsilon_{0}\overrightarrow{E}$