Consider the following statements:
1. Boiling of water from a heat source at the same boiling temperature
2. Theoretical isothermal compression of a gas
3. Theoretical polytropic compression process with heat rejection to atmosphere
4. Diffusion of two ideal gases into each other at constant pressure and temperature
Which of these processes are irreversible?
(A) 1, 2, 3 and 4 (B) 1 and 4 only
(C) 2, 3 and 4 (D) 3 and 4 only