The correct answer is C. the.
The Indus River is the longest river in India. It is also the longest river in Pakistan and the second-longest river in Asia, after the Yangtze River. The Indus River originates in the Tibetan Plateau in China and flows through India and Pakistan into the Arabian Sea. The Indus River is a major source of water for irrigation and drinking water in India and Pakistan. It is also a major transportation route.
The word “the” is used before a noun that is specific or unique. In this case, the Indus River is the specific river that is being discussed. The other options, “a” and “an”, are used before nouns that are general or non-specific. For example, you would say “I saw a dog” if you saw any dog, but you would say “I saw the dog” if you were referring to a specific dog.
The option “None of the above” is not correct because the Indus River is a specific river.