Question

The __________ shoe department is on the other side of the store.

A.
mens'

B.
mens

C.
men's

Answer 1

The men's shoe department is on the other side of the store. It is already plural. 

Answer 2

C. Men's
The men's shoe department is on the other end of the store.
It is spelled this way because you are saying it is a men's store. It belongs to the men. I looked it up. It would NOT be mens, because that is not even a word. Men is already plural. It would not be mens' because men is already plural. Hope this helps!!! (: