Answer : Option D

Explanation :

$MF#%
\boxed{\text{If a car covers a certain distance at x kmph and an equal distance at y kmph,}\\
\text{the average speed of the whole journey = }\dfrac{2xy}{x+y}\text{ kmph}}\\
\begin{align}
&\text{Hence, average speed = }\dfrac{2 \times 3 \times 2}{2 + 3} = \dfrac{12}{5}\text{ km/hr}\\\\
&\text{Total time taken = }5\text{ hours}\\
&\Rightarrow \text{Distance travelled} = \dfrac{12}{5} \times 5 = 12\text{ km}\\
&\Rightarrow \text{Distance between his house and office =}\dfrac{12}{2}=6\text{ km}
\end{align} $MF#%