Select the option that converts the given sentence into the superlative degree.
The river Ganga has some of the purer water on earth.

Correct option is D

The correct superlative form is (d).
Explanation: The superlative degree of “pure” is “purest,” which is used when comparing the quality of one against all others.
“Some of the purest” indicates that the Ganga's water is among the most pure on earth.
Grammatical Rule Used: Superlative adjectives in English for single-syllable adjectives are formed by adding “-est” to the adjective base, such as “pure” becoming “purest.”