Which of the following is equivalent to \( \frac{1}{\left(\frac{1}{x+4}\right)+\left(\frac{1}{x+5}\right)} \) if \( x>0 ? \) A. \( 2 x+9 \) B. \( x^{2}+9 x+20 \) C. \( \frac{2 x+9}{x^{2}+9 x+20} \) D.