For a pure substance, the melting point ($T_B$) and freezing point ($T_A$) are the same, i.e., $T_A = T_B$. As the temperature increases, the entropy of the substance also increases. At the melting point, the substance undergoes a phase transition from solid to liquid. During this process, heat is absorbed at a constant temperature, leading to a sudden and discontinuous increase in entropy (since the liquid state is more disordered than the solid state). After the melting is complete, the entropy of the liquid continues to increase with temperature. The correct graph would show a steady increase, a vertical jump in entropy at $T_A = T_B$, and then a continued increase.