10. Which of the following statements is correct?

A. A firm can operate in either the short run or the long run.

B. While a firm's plant size could be too small in the long run, its size cannot be too small in the short run.

C. A firm can enjoy economies of scale in either the short run or the long run.

D. While a firm can plan as if it is in the long run, it can operate only in the short run.