In the Mond process for nickel refining, which statements are correct?

Impure Ni reacts with CO at about $330$-$350\mathrm{K}$ to form volatile $\mathrm{Ni}(\mathrm{CO}){}_4$ (A). The vapour is heated to about $450$-$470\mathrm{K}$ and decomposes to pure Ni (B). The forward reaction is exothermic with negative $\Delta S$, so it is favoured at low temperature; saying it is endothermic (C) is false. The net result is transport of Ni as a volatile compound leaving non-volatile impurities behind (D). Correct: A, B, D.