Concept:Total fixed cost remains constant at all output levels, so its curve is a straight horizontal line.
Explanation:Fixed costs do not change when output changes.
Examples include rent, insurance, and depreciation.
Let output be measured on the horizontal axis and total fixed cost on the vertical axis.
Since total fixed cost is constant, the curve is parallel to the output axis.
Hence, it is a horizontal line, not vertical or sloping.
Answer:A. horizontal