Consider the following statements:
(1) Free expansion of a gas
(2) Slow heating of oil from a constant temperature source
(3) Evaporation of water at its saturation temperature by a source at the same temperature
(4) Isentropic compression of an ideal gas
Which of these processes are irreversible?
(A) 1 and 2 (B) 2 and 3
(C) 3 and 4 (D) 1 and 4