Out of the following four dimensional quantities,which one is called a dimensional constant?

Match the following two columns:

Column-$I$	Column-$II$
$(A)$ Electrical resistance	$(p)$ $M L^3 T^{-3} A^{-2}$
$(B)$ Electrical potential	$(q)$ $M L^2 T^{-3} A^{-2}$
$(C)$ Specific resistance	$(r)$ $M L^2 T^{-3} A^{-1}$
$(D)$ Specific conductance	$(s)$ None of these

The dimensional formula ${M^0}{L^2}{T^{ - 2}}$ stands for

Turpentine oil is flowing through a tube of length $l$ and radius $r$. The pressure difference between the two ends of the tube is $P$. The viscosity of oil is given by $\eta = \frac{P(r^2 - x^2)}{4vl}$,where $v$ is the velocity of oil at a distance $x$ from the axis of the tube. The dimensions of $\eta$ are

The dimensions of permeability of free space $(\mu_0)$ can be given by:

Which two of the following five physical parameters have the same dimensions?
$(a)$ Energy density
$(b)$ Refractive index
$(c)$ Dielectric constant
$(d)$ Young's modulus
$(e)$ Magnetic field