Choose the option that best completes the gap in the sentence. Are those girls friends of _____?

The correct choice to complete the sentence is "yours."

Here's the explanation:

• "your's" is incorrect because the apostrophe indicates possession, but in standard English, the word "yours" is already the possessive pronoun, so no apostrophe is needed.


• "your" is a possessive adjective used before a noun, for example, "your book." Since the sentence is asking about the pronoun referring to the owner of the friends, "your" is not appropriate.
• "yours'" is incorrect because it attempts to pluralize or possess a form that is already possessive. "Yours" is the correct possessive pronoun and does not need an apostrophe.
• "yours" is the correct answer. It is the possessive pronoun which indicates that something belongs to "you." In this context, it functions correctly to refer to the ownership of the friends being inquired about.

Therefore, the sentence should read: "Are those girls friends of yours?"