Q.Identify the flow variable.

Income is measured over a period of time, making it a flow variable; the answer is (a).

In the introduction to macroeconomics of the Tamil Nadu HSC Commerce syllabus, variables are classified as:

• Stock variables — measured at a particular point of time (no time dimension), e.g. money supply on a date, foreign-exchange reserves on a date, wealth or assets held.
• Flow variables — measured over a period of time (per hour, per month, per year), e.g. income, consumption, investment, saving. …