Concept:The official document that grants the power to spend public money is called a warrant.Explanation:The legislature first approves the budget and the votes contained in it. This approval only permits spending up to certain limits. To actually release money or incur expenditure, a separate official order is required. In public sector accounting, that order is known as a warrant. It is issued by the competent authority to the spending officer.Thus, the authority to incur expenditure in the public sector is a warrant, not the vote, budget, or voucher.Answer:A. warrant