The reaction (A(mathrm{l}) ightarrow R(mathrm{~g})) is allowed to reach equilibrium condition in an autoclave. At equilibrium

The reaction \(A(\mathrm{l}) \rightarrow R(\mathrm{~g})\) is allowed to reach equilibrium condition in an autoclave. At equilibrium there are two phases - one a pure liquid phase of \(A\) and the other a vapour phase of \(A, R\) and \(S\). Initially \(A\) alone is present. The number of degrees of freedom is

(a) 1

(b) 2

(c) 3

(d) 0.