If a Manufacturer Has a U-Shaped Long-Run Average Total Cost

If a manufacturer has a U-shaped long-run average total cost curve, then

A) it cannot correctly calculate the position of its fixed cost curve
B) there is an output level such that producing one more unit increases average total cost
C) there must be a large range of production over which the firm experiences constant returns to scale
D) no two quantities of output can have the same average total cost
E) there does not exist an output level such that producing one more unit decreases average total cost