Explanation:

- The Ashtadhyayi of Panini is a foundational text in the study of Sanskrit grammar.

- It systematically outlines the rules and structure of Sanskrit, containing over 3,900 sutras.

- Option 1: Mauryan Polity refers to the political structure during the Mauryan Empire, not related to the Ashtadhyayi.

- Option 2: Gupta Administration revolves around governance during the Gupta Empire, again unrelated to the text.

- Option 3: Medicine involves medical practices and knowledge, distinct from grammatical studies.

- Option 4: Sanskrit Grammar - This is the correct domain of Panini's Ashtadhyayi.

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