Concept:
Maxwell thermodynamic relations are obtained from thermodynamic potentials.
Step 1: Recall the correct relation involving pressure and entropy.
One Maxwell relation is:
\[
\left(\frac{\partial S}{\partial P}\right)_T=-\left(\frac{\partial V}{\partial T}\right)_P
\]
Step 2: Compare with option (C).
Option (C) gives:
\[
\left(\frac{\partial S}{\partial P}\right)_T=\left(\frac{\partial V}{\partial T}\right)_P
\]
Here, the negative sign is missing.
Step 3: Final answer.
Therefore, option (C) is the incorrect Maxwell relation.
\[
\therefore \text{Correct Answer is (C)}
\]