A sensitivity of transfer function $$T = \frac{{{A_1} + k{A_2}}}{{{A_3} + k{A_4}}}$$   with respect to parameter k is given by

A. $$\frac{{k\left( {{A_2}{A_3} - {A_1}{A_4}} \right)}}{{\left( {{A_3} + k{A_4}} \right)\left( {{A_1} + k{A_2}} \right)}}$$

B. $$\frac{{\left( {{A_2}{A_3} - {A_1}{A_4}} \right)}}{{{{\left( {{A_3} + k{A_4}} \right)}^2}}}$$

C. $$\frac{{k\left( {{A_2}{A_3} - {A_1}{A_4}} \right)}}{{{{\left( {{A_3} + k{A_4}} \right)}^2}}}$$

D. $$\frac{{\left( {{A_2}{A_3} - {A_1}{A_4}} \right)}}{{\left( {{A_3} + k{A_4}} \right)\left( {{A_1} + k{A_2}} \right)}}$$

Answer: Option A