The graph on the left is correct. Both graphs correctly
indicate that the heat capacity at low temperatures,
when the protein is folded, is lower than the heat
capacity at high temperatures, when the protein is
unfolded. However, the heat capacity of a protein peaks
at its melting temperature because relatively more
energy goes into breaking intramolecular interactions.
It then decreases at higher temperatures when fewer
unbroken interactions persist. Only the left graph
indicates this correctly.