Which of the following pairs is correctly matched with Al-Biruni's re…

The correct answer is Option (1) → Sanskrit - a language of enormous range, both in words and inflections

Option (1) Sanskrit - a language of enormous range, both in words and inflections — Correct. Al-Biruni said Sanskrit had an enormous range, both in words and inflections. Inflections are the changing endings of a word.

Option (2) Persian - a language into which Sanskrit ideas passed easily — Incorrect. He held the opposite: Sanskrit was so different from Arabic and Persian that ideas could not be easily translated.

Option (3) Arabic - a language with one fixed name for each thing — Incorrect. He compared Sanskrit to Arabic because both call one and the same thing by various names. Arabic did not have one fixed name per thing.

Option (4) Works of Brahmanas - sources he avoided for Indian society — Incorrect. He depended almost exclusively on Brahmana works such as the Vedas, Puranas and Manusmriti to understand Indian society.