Explanation:

- Flexible Budget: Adapts to changes in activity level. It adjusts costs based on actual performance, making it suitable for variable circumstances.

- Functional Budget: Pertains to a specific function or department within an organization, like production or marketing. A plant utilisation budget, which deals with the operational capacity of a plant, falls into this category.

- Current Budget: Usually refers to short-term financial planning, focusing on immediate revenues and expenses without expanding long-term horizons.

- Master Budget: Consolidates various functional budgets to provide a comprehensive financial overview of the organization.

Your correct answer: Functional Budget