Answer:
upward sloping to reflect increasing opportunity cost.
Explanation:
Marginal cost curve represents the change on total cost when the output is increased by one unit, it is the cost of producing extra unit of output.
The marginal cost curve is usually upward sloping because of the occurrence of diminishing marginal returns. As production increases it costs more to produce extra units so marginal cost curve increases.
This is illustrated in the attached diagram where marginal cost falls slightly and begins to rise continuously till it goes higher than revenue.
