Degree of freedom of a system consisting of a gaseous mixture of H2 and NH3 will be

Answer: Option D

Given, number of components $$=2$$
Number of phases $$=1$$
So, degree of freedom
$$\begin{array}{l}f=C-\varnothing +2\\ \Rightarrow 2-1+2\\ \Rightarrow 3\\ F=3\end{array}$$