The correct answer is C. little.
A few means “a small number of”. It is used to refer to a number of things that is less than a dozen, but more than one. For example, you might say “I have a few friends” or “I have a few questions”.
Little means “a small amount of”. It is used to refer to a quantity of something that is less than a lot, but more than none. For example, you might say “I have little money” or “I have little time”.
In the sentence “I had to walk 5 km yesterday as I had little rupees for fare”, the speaker is saying that they did not have enough money to pay for a ride. The word “little” is used to emphasize the fact that they had very little money.
The other options are incorrect because they do not accurately convey the meaning of the sentence. The word “few” would suggest that the speaker had a small number of rupees, but not so few that they could not afford a ride. The word “a few” would suggest that the speaker had a small number of rupees, but not so few that they had to walk 5 km.