Consider the following statements :

1. Milk and sugar is a homogeneous system.

2. Free expansion is an irreversible process 3. Thermos flask is an isolated system.

Of these statements :

(a) only 1 is correct

(b) 1 and 2 are correct

(c) 2 and 3 are correct

(d) 1,2 and 3 are correct.