Answer : Option D

Explanation :

$MF#%\begin{align}
&\text{Total distance travelled = 10 + 12 = 22 km}\\\\
&\text{Time taken to travel 10 km at an average speed of 12 km/hr = }\dfrac{\text{distance}}{\text{speed}} = \dfrac{10}{12}\text{ hr}\\
&\text{Time taken to travel 12 km at an average speed of 10 km/hr = }\dfrac{\text{distance}}{\text{speed}} = \dfrac{12}{10}\text{ hr}\\
&\text{Total time taken =}\dfrac{10}{12} + \dfrac{12}{10}\text{ hr}\\\\
&\text{Average speed = }\dfrac{\text{distance}}{\text{time}} = \dfrac{22 }{\left(\dfrac{10}{12} + \dfrac{12}{10}\right)} = \dfrac{22 \times 120 }{\left(10 \times 10\right) + \left(12 \times 12\right)}\\
&\dfrac{22 \times 120 }{244}=\dfrac{11 \times 120 }{122}=\dfrac{11 \times 60}{61}=\dfrac{660}{61}\approx 10.8\text{ kmph}
\end{align} $MF#%