The process with negative entropy change is:

Explanation-

Due to dissolution to form an aqueous solution entropy increases.

                             N2 + 3H2    2NH3

Entropy change(S) = nP - n R

                                            = 2 - 4
 
                                            = -2

Hence, entropy decreases in the synthesis of ammonia from N2 and H2.

In dissociation of CaSO4(s) to CaO(s) and SO3(g), a solid is converted into gas thus entropy decreases.

In the sublimation of dry ice also as solid is converted into gas thus entropy decreases.

Final Answer:
Hence, Option (B) is correct.