The correct answer is C. public expenditure in excess of public revenue.
Deficit financing is a situation in which a government spends more money than it receives in revenue. This can be done by borrowing money, printing new money, or using other methods. Deficit financing can be used to stimulate the economy during a recession, but it can also lead to inflation.
Option A is incorrect because printing new currency notes does not necessarily mean that there is a deficit. For example, a government might print new currency notes to replace worn out or damaged notes.
Option B is incorrect because replacing new currency with worn out currency does not necessarily mean that there is a deficit. For example, a government might replace new currency with worn out currency to keep the money supply stable.
Option D is incorrect because public revenue in excess of public expenditure is called a surplus. A surplus can be used to pay down debt, invest in infrastructure, or provide tax breaks.