System A consists of a deuterium molecule, D2 , and an oxygen atom, O, confined within a fixed-volume container. System B consists of a heavy water molecule, D2O, confined within a container identical to that of system A. System C consists of a tritium atom, T, a neutron, n, and an oxygen atom, O, within another container again identical to that of system A.

(a) Are systems A, and C identical? If not, can you define a system so that systems A, B, and C are identical but each is in a different state?

(b) Can you define a system that is at once identical to systems A and B, but not C?

(c) Can you define a system that is at once identical to systems A and C, but not B? If so, are the states of A and C identical?