Final answer:
The correct possessive form to complete the sentence is 'The men's locker room is closed.' We use a) 'men's' since 'men' is an irregular plural noun and the possessive is formed by adding an apostrophe and an s.
Step-by-step explanation:
To choose the correct form of the word to complete the sentence 'The ________ locker room is closed', we need to decide which possessive form is correct for the plural noun 'men'. The correct option is 'a) Men's'. The possessive form of a plural noun that ends in -s is typically formed by just adding an apostrophe after the s.
However, the noun 'men' is an irregular plural, so we actually add an apostrophe and then an s ('men's') to show possession.
The sentence correctly filled would be: The men's locker room is closed.
It's important to remember these rules for possessive forms because they help us write clearly and correctly, indicating ownership or association.