Identify the flow variable from the following:

Option 1: Annual Expenditure of a school -> Flow variable as it is measured over a period of time (one year).

Option 2: Distance between Punjab and Haryana -> This is a physical measurement, not an economic variable.

Option 3: Bank balance of Mr. Mukesh as on 31st March 2023 -> Stock variable as it is measured at a specific point in time.

Option 4: Investment of Mr. Mohit as on 31st December 2023 -> Stock variable as it is measured at a specific point in time.

Hence, Option 1: Annual Expenditure of a school -> A flow variable is measured over a period of time, while a stock variable is measured at a particular point in time. Annual expenditure refers to the total spending over the course of one year, making it a flow variable. The other options (bank balance and investment 'as on' specific dates) are stock variables as they represent values at a particular moment. -> correct