Which of the Following Statements Is Correct

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.