The value of $p$ for which vectors $\hat{i} + 2\hat{j} + 3\hat{k}$ and $2\hat{i} - p\hat{j} + \hat{k}$ are perpendicular to each other is (A) $0$ (B) $1$ (C) $\frac{5}{2}$ (D) $-\frac{5}{2}$