Which of the following statements pertaining to entropy are correct?
1. The entropy of a system reaches its minimum value when it is in a state of equilibrium with its surroundings.
2. Entropy is conserved in all reversible processes
3. Entropy of a substance is least in solid phase.
4. Entropy of a solid solution is not zero at absolute zero temperature
(a) 1, 2 and 3 only (b) 2,3 and 4 only
(c) 3 and 4 only (d) 1,2,3 and 4