Final answer:
In the long run, a firm can change the amount of labor and capital that it employs. Therefore, the correct option is A.
Step-by-step explanation:
In the long run, a firm can change the amount of labor and capital that it employs. This is a basic assumption of the long run. In contrast, in the short run, firms cannot change the amount of fixed inputs, such as capital. Therefore, option (a) 'can change the amount of labor and capital that it employs' is the correct answer.