Final answer:
The sale of an Airbus by an airline to the Air Force would count towards GDP as government expenditure, as it is a purchase of goods and services by the government. The correct option is 2. government expenditure.
Step-by-step explanation:
When an airline sells an Airbus to the Air Force, this transaction would be included in the calculation of Gross Domestic Product (GDP) under government expenditure.
GDP is a measure of economic activity and encompasses various components such as consumption, business investment, government spending on goods and services, and net exports.
When the government, in this case, the Air Force, purchases goods such as an aircraft, it counts as government spending on goods and services which is a part of government purchases.
Government purchases are one of the components of GDP from the demand side, which also includes consumer spending, investment, and net exports (exports minus imports).
Government expenditures do not include transfer payments like Social Security or unemployment benefits because these are not payments for goods or services, but rather redistributions of income. The correct option is 2. government expenditure.