Which of the following result(s) in a decrease in the entropy of the system?

I. NH₃(1 atm, 298 K) → NH₃(3 atm, 298 K)
II. Br₂(g) → Br₂(l)
III. NaBr(s) → Na₊(aq) + Br₋(aq)
IV. O2(g, 298 K) → O₂(g, 373 K)