Answer:
A. do not affect, and are not affected by, the quantity the firm produces
Explanation:
In a short run shutdown, regardless of the production of volume or if there is any production at all, fixed costs still have to be paid in full and therefore are irrelevant in the decision about whether to shut down production in the short run.
Thus, the answer is A. do not affect, and are not affected by, the quantity the firm produces.