The correct option is A It was considered a source of income for the State, a sort of tax paid by the people.
Vishti was considered as a source of income for the state, a sort of tax by the people. Junagarh inscription mentions Vishti as one form of tax, which indicates that it was extracted from Gujarat and Malwa region.
Anyone could be sent as a labourer for Vishti, not necessarily the eldest son of the labourer. The forced labourers were not entitled to any weekly wages.