Question:

Which of the following sentences is grammatically correct?

A Their concern is that there may not be enough appetizers for everyone they’re expecting at the cocktail party.

Explaination

“Their” is a pronoun used to refer to a group of people. Since the “concern” belongs to a group of people, we’d use the word “their” to explain the possessive meaning. The word “they’re” is a contraction of “they are.”