For a reaction involving only gases at 25?C the equilibrium constant can be expressed in terms of molarity Ke or partial pressure Kp. Which is true about the numerical value of Kp ?

A. Kc is generally greaer than Kp
B. Kc is generally less than Kp
C. Kc is generally equal to Kp
D. Kc is equal to Kp if the total moles of reactants and products are equal