The net change in the internal energy of a cyclic process is zero because it returns to its original temperature after each cycle. This means that statement I is correct.
The total change in entropy is zero for any reversible cycle. This means that statement II is correct as the gas returns to its original state each cycle.
The graph is for a heat engine, which takes in heat and does work on the environment. Therefore statement III is incorrect. A clockwise cycle always does net positive work on the environment.
