Correct Answer: 21.78 km/hr

Solution : Use the formula, $\text{Average speed}=\frac{\text{Total distance}}{\text{Total Time taken}}$
The time needed to go from city A to city B $=\frac{80}{16}=5$ hours
The time needed to go from city B to city C $=\frac{120}{40}=3$ hours
The time needed to go from city C to city D $=\frac{90}{20}=4.5$ hours
The time needed to go from city D to city E $=\frac{60}{30}=2$ hours
The time needed to go from city E to city  F $=\frac{42}{12}=3.5$ hours
The total distance from City A to City F = 80 + 120 + 90 + 60 + 42 = 392 km
The total time to cover city A-F = 5 + 3 + 4.5 + 2 + 3.5 = 18 hours
The approximate average speed of the person while travelling from city A to city F
$=\frac{392}{18}=21.78$ km/hr
Hence, the correct answer is 21.78 km/hr.