c
Water has highest density at $4^{\circ} C$. This changes its properties from other simple fluids.
When water is heated from $0^{\circ} C$ to $4^{\circ} C$, the volume of liquid decreases.
Thus for this transition, $P \Delta V$ is negative.
$\int C_p d T=\int C_V d T+P \Delta V$
$\Rightarrow C_P < C_V$