Equilibrium Constants for Gases Can Be Expressed in Terms of Concentrations

Equilibrium constants for gases can be expressed in terms of concentrations, K_c, or in terms of partial pressures, K_p. Which one of the following statements regarding K_c and K_p is correct?

A) K_c and K_p are equal when all stoichiometric coefficients in the balanced reaction equation equal one.
B) K_c and K_p have the same values but different units.
C) K_c and K_p are equal when the sum of the stoichiometric coefficients for the products equals the sum of the stoichiometric coefficients for the reactants.
D) K_c and K_p can never be equal.
E) K_c and K_p are equal when the conditions are standard (P = 1 atm, T = 298 K) .