Graph 13-6 This Graph Depicts Average Total Cost Functions for Functions

Graph 13-6
This graph depicts average total cost functions for a firm that produces automobiles. Use the graph to answer the following question(s) .
-Refer to Graph 13-6. If the firm is currently operating on ATC_B, what options does it have if it wants to change its level of automobile production over the next couple of weeks?

A) the firm has no options. It cannot change output level in the short run
B) it can operate at any level of output between points M and N
C) it can operate at any level of output, as long as it stays on ATC_D
D) it can operate at any level of output as long as it stays on ATC_B