Ans: A
$\begin{array}{rcl}
f(3)f(\dfrac{1}{3}) & = & \dfrac{3}{1+3} \times \dfrac{\frac{1}{3}}{1+\frac{1}{3}} \\
& = & \dfrac{3}{4} \times \dfrac{1}{3} \div \dfrac{4}{3} \\
& = & \dfrac{3}{16}
\end{array}$
$\begin{array}{rcl}
f(3)f(\dfrac{1}{3}) & = & \dfrac{3}{1+3} \times \dfrac{\frac{1}{3}}{1+\frac{1}{3}} \\
& = & \dfrac{3}{4} \times \dfrac{1}{3} \div \dfrac{4}{3} \\
& = & \dfrac{3}{16}
\end{array}$
