Option a is the correct answer. These are different terms for measuring land during the Gupta period. The Kulyavapa, Dronavapa, Adhavapa are the terms related to land measurements mainly mentioned in the copper plate inscriptions of Gupta era that were found in Bengal. Kulyavapa land must have been equal to around 160 bighas of land. A Dronavapa must be 16-20 bighas and Adhvapa which appears to be the smallest must be around 4 − 5 4−5 bighas of land.