Explanation:

- When the output is zero, variable costs are also zero because they change with the level of output.

- Correct Answer: Option 2 - zero

- Variable costs are costs that vary directly with the level of output, such as materials and labor.

- If no goods are produced, there's no need for materials or production labor, hence variable costs will be zero.

- Option 1 (constant) is incorrect because fixed costs are constant, not variable costs.

- Option 3 (minimum) is incorrect because minimum implies there's some positive cost, which isn't true at zero output.

- Option 4 (maximum) is incorrect as variable costs cannot be maximum at zero output.