The correct answer is: A. lie above the ATC curve.
The average total cost (ATC) curve is a graph that shows the average cost of producing a product as the quantity produced increases. The marginal cost (MC) curve is a graph that shows the additional cost of producing one more unit of a product.
If the ATC curve is a rising straight line, then as output expands, the MC curve will lie above the ATC curve. This is because the additional cost of producing one more unit of a product will always be greater than the average cost of producing all the units that have already been produced.
Here is a diagram that illustrates the relationship between the ATC curve and the MC curve:
[Diagram of ATC and MC curves]
The ATC curve is the blue line, and the MC curve is the red line. The MC curve lies above the ATC curve at all points. This is because the additional cost of producing one more unit of a product is always greater than the average cost of producing all the units that have already been produced.
I hope this explanation is helpful! Please let me know if you have any other questions.