Which of the following is true for a thermodynamic system

1. for isothermal process (U) internal energy= const  ⇒ΔU=0  2. W=nRγ−1T1−T2,W≠0   For adiabatic process  3. (U) internal energy & (S) entropy depends only on initial and final states, and independent of path  4. (S) entropy always increases for a process. It is zero in fully reversible.