Which of the following is a stock variable?

Stock Variable -A stock is a quantity which is measurable at a particular point of time. Example - Capital is a stock variable. On a particular date (say, 31srtMarch, 2017), a country owns and stock of machines, buildings, roads, ports, foreign debts, loan, inventories, money supply, population, Balance Sheet etc. Flow Variables - A flow is a quantity which is measured with reference to a period of time. Example- Monthly salary, Change in the money supply, Profit and Loss of a company during a period, Export and Import during the year.