Consider the following statements:
1. Slow heating of water from an electrical heater
2. Isentropic expansion of air
3. Evaporation of a liquid from a heat source at the evaporation temperature
4. Constant pressure heating of a gas by a constant temperature source
Which of these processes is/are reversible?
(A) 3 only (B) 2 and 3 only
(C) 2 and 4 only (D) 1, 2, 3 and 4