A.
At high temperatures, the – TΔS mix term dominates, and the free energy curve resembles that of the ideal solution.
B.
As the temperature decreases, the Δh mix term and the – TΔS mix term become similar in magnitude and the resulting free energy curve shows two minima and a central maximum.
C.
For compositions outside C-D range, the solid solution will still be stable as a single phase since it has a lower free energy than a mixture of two phases.