Which of the Following Statements Is True

Multiple Choice

Which of the following statements is true?

A) The number of firms in the industry is fixed in the short run, but the number can change in the long run.
B) Free entry and exit of firms is possible in the short run, but the entry and exit of firms is restricted in the long run.
C) The short-run average cost curves lies below the long-run average cost curves in both the short run and the long run.
D) A firm can vary all its factors of production in both the short run and the long run.