Under Article IX-D, Section 2(2), the Commission on Audit has exclusive authority to promulgate rules for the prevention and disallowance of expenditures that are:

The correct answer is B. Irregular, unnecessary, excessive, extravagant or unconscionable

Section 2(2) lets COA define the scope of its audit and issue accounting and auditing rules, including rules against irregular, unnecessary, excessive, extravagant or unconscionable expenditures, or uses of government funds and property.