U-shaped curves in economics refer to the graphical representation of the relationship between a cost or a benefit and the level of output. The shape of the curve is due to the law of diminishing marginal returns, which states that as more units of a variable input are added to a fixed input, the marginal output (or benefit) from each additional unit of the variable input will eventually decrease.

AVC Curve
The Average Variable Cost (AVC) curve is a U-shaped curve that shows the average variable cost of production at different levels of output. This curve includes both variable costs (e.g. labor, raw materials) and fixed costs (e.g. rent, equipment), but only the variable costs vary with the level of output. As output increases, the AVC curve initially decreases due to economies of scale, but eventually increases due to diseconomies of scale.

AC Curve
The Average Cost (AC) curve is also a U-shaped curve that shows the average cost of production at different levels of output. This curve includes both variable and fixed costs, and is calculated by dividing the total cost by the level of output. Like the AVC curve, the AC curve initially decreases due to economies of scale, but eventually increases due to diseconomies of scale.

MC Curve
The Marginal Cost (MC) curve is a U-shaped curve that shows the additional cost of producing one more unit of output. This curve intersects both the AVC and AC curves at their minimum points, as the marginal cost is equal to the average cost at this point.

AFC Curve
The Average Fixed Cost (AFC) curve, unlike the other curves mentioned above, is not a U-shaped curve. This curve shows the fixed cost per unit of output, and decreases as output increases due to the spreading of fixed costs over a larger number of units.

Therefore, the correct answer is option B, AFC curve, as it is not a U-shaped curve.

TFC remains constant throughout production. So AFC continuously decrease with production and is rectangular hyperbola and never U shaped