One Reason That Firms Hire Labor at the Point Where

One reason that firms hire labor at the point where w = MPN is

A) if w < MPN, the cost (w) of hiring additional workers exceeds the benefits (MPN) of hiring them, so they should hire fewer workers.
B) if w > MPN, the cost (w) of hiring additional workers is less than the benefits (MPN) of hiring them, so they should hire more workers.
C) if w < MPN, the cost (w) of hiring additional workers equals the benefits (MPN) of hiring them, so they have the right number of workers.
D) if w > MPN, the cost (w) of hiring additional workers exceeds the benefits (MPN) of hiring them, so they should hire fewer workers.