A U-Shaped Long-Run Average Total Cost Curve Can Be Explained

Multiple Choice

A U-shaped long-run average total cost curve can be explained by firms increasing their size to do which of the following?
(i) take advantage of greater specialisation
(ii) avoid coordination problems
(iii) avoid fixed costs

A) (i) and (ii)
B) (ii) and (iii)
C) (i) only
D) (i) , (ii) and (iii)