Identify the Radicand $4 \mathrm{ab} \sqrt{\mathrm{b}^{2}-9}$ A) $b^{2}$ B) $\sqrt{b^{2}-9}$ C) $b^{2}-9$ D) $4 \mathrm{ab}$

Identify the radicand.
- $4 \mathrm{ab} \sqrt{\mathrm{b}^{2}-9}$

A) $b^{2}$
B) $\sqrt{b^{2}-9}$
C) $b^{2}-9$
D) $4 \mathrm{ab}$