Answer: Option C
To find out what portion of the whole distance the person covers on foot, we need to first calculate the distance covered on foot.
We know that the total distance traveled is 3.5 km, and the person covered 1 2/3 km on bicycle and 1 1/6 km on scooter.
Therefore, the distance covered on foot can be calculated as follows:
Distance covered on foot = Total distance traveled - Distance covered on bicycle - Distance covered on scooter= 3.5 - 1 2/3 - 1 1/6= 3.5 - (5/3 + 7/6)= 3.5 - (10/6 + 7/6)= 3.5 - (17/6)= (21/6) - (17/6)= 4/6= 2/3 km
Now, we can find out what portion of the whole distance the person covered on foot by dividing the distance covered on foot by the total distance traveled:
Portion covered on foot = Distance covered on foot / Total distance traveled= 2/3 / 3.5= 6/21= 2/7
Therefore, the correct answer is option C, 4/21, which is equivalent to 2/7.
Formula used:

• To calculate the distance covered on foot: distance covered on foot = total distance traveled - distance covered on bicycle - distance covered on scooter
• To calculate the portion of the whole distance covered on foot: portion covered on foot = distance covered on foot / total distance traveled

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