Transform the following expression into an algebraic expression in $x$ . Assume that the inverse trigonometric function is defined for its argument and assume that $x>0$ .
$\sec\left(\cot^{-1}\frac{\sqrt{25-x^2}}{x}\right)$

• A. $\frac{5\sqrt{25-x^2}}{25+x^2}$
• B. $\frac{x\sqrt{25-x^2}}{25-x^2}$
• C. $\frac{5\sqrt{25-x^2}}{25-x^2}$
• D. $\frac{5\sqrt{x^2-25}}{x^2-25}$