Supply is________

1. Analyze the question The question asks what supply is, in economic terms. The options use the stock vs. flow distinction, so we need to recall how economists classify supply.

2. Explain the concept

• A stock is a quantity measured at a single point in time (e.g., the amount of money in your bank account today, or the total number of bags of cement in a warehouse right now).
• A flow is a quantity measured over a period of time (e.g., monthly salary, 500 bags of rice supplied per week).

Supply is defined as the quantity of a good or service that producers are willing and able to offer for sale at a given price over a given period of time. Examples: "100 bags of garri per day" or "2,000 litres of fuel per week". Because it always carries a time dimension, supply is a flow concept.

3. Solution, option by option

• A. A stock: Incorrect. A stock has no time period attached. Note that the amount of goods actually available at one moment is "stock", but supply itself is not.
• B. A flow: Correct. Supply is measured per unit of time (per day, week, month, or year).
• C. Constant: Incorrect. Supply changes when price, cost of production, technology, taxes, etc. change.
• D. A table: Incorrect. A supply schedule is a table, but supply itself is not a table.

4. Answer The correct option is B. A Flow.

5. Tip Ask yourself, "Is there 'per time' attached?" If yes, it is a flow. Supply and demand are both flow concepts, so remember "per week, per month" whenever you see them. Do not confuse supply with a "supply schedule" (the table) or with "stock" (what is sitting in the warehouse).