Zeroth Law of thermodynamic state that
(a) Two thermodynamic systems are always in thermal equilibrium with each other
(b) If two systems are in thermal equilibrium, then the third system will also be in thermal equilibrium
(c) Two systems not in thermal equilibrium with a third system will also not thermal equilibrium with each other
(d) When two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other