The correct choice is (b) Directly proportional to relative permittivity
For explanation: Transition capacitance is the capacitance exhibited by a diode due to the p-side and n-side of the diode is separated by a distance of depletion width same as in an electrolytic capacitor.
The equation of transition capacitance = ƸA/W
Where Ƹ = permittivity of the material of diode, W = depletion width
A = area of cross section
Relative permittivity is directly proportional to the permittivity of the material.