The square root of ( 7 + 3 5 ) ( 7 - 3 5 ) is ?

Answer: Option B

$$\begin{array}{rl}& =\sqrt{\left(7+3\sqrt{5}\right)\left(7-3\sqrt{5}\right)}\\ & =\sqrt{{\left(7\right)}^2-{\left(3\sqrt{5}\right)}^2}\\ & =\sqrt{49-45}\\ & =\sqrt{4}\\ & =2\end{array}$$