Answer: A - Economics of Scale
Step-by-step explanation:
The long-run average total cost curve shows the lowest average cost that is possible to produce each output in the long run.
The Long Run Average Total Cost is divided into three segments:
a. The downward-sloping part which reflects economies of scale.
b. The flat portion part which reflects constant returns to scale.
c. The upward-sloping part which reflects diseconomies of scale.
I hope my answer helps.