A​ firm's short-run average cost curve is​ U-shaped. Which of these conclusions can be reached regarding the​ firm's returns to​ scale?
A. The firm experiences​ increasing, constant, and decreasing returns in that order.
B. The firm experiences first​ decreasing, then increasing returns to scale.
C. The firm experiences increasing returns to scale.
D. The​ short-run average cost curve reveals nothing regarding returns to scale.