Correct answer: B. Transfer of land rights and revenue
Explanation: Direct answer: Option B, transfer of land rights and revenue. A land grant inscription records that a ruler gave land, or rights connected with it, to a person or institution. Such grants could include the right to collect revenue and sometimes administrative or customary privileges. They therefore help historians study changes in ownership, control, taxation and rural society during the Gupta period. Option B is correct because it directly describes what these records indicate. Option A, naval warfare, would require military records and is not the main meaning of land-grant inscriptions. Option C, reading the Indus script, concerns a much earlier civilisation and is unrelated to Gupta grants. Option D, Mauryan pillar polish, describes an artistic and technological feature from an earlier period, not the transfer of land or revenue. Memory cue: land grant means land plus rights, income or revenue—not merely a piece of ground.