The displacement current is a quantity that appears in Maxwell's equations. It is proportional to the rate of change of the electric flux \(\phi_E\). The general form of the displacement current is:
\[
I_d = \mu_0 \epsilon_0 \frac{d\phi_E}{dt}
\]
where \(\mu_0\) is the permeability of free space, \(\epsilon_0\) is the permittivity of free space, and \(\frac{d\phi_E}{dt}\) is the time rate of change of the electric flux.
Thus, the correct option is:
\[
\mu_0 \epsilon_0 \frac{d\phi_E}{dt}
\]