Which sentence shows the correct use of a common homophone?

Question

They’re still not finished with the project that was due yesterday.
Their are a number of great books about the Civil War in the library.
They said they would put away all of there clean clothes before school.
I think I saw an entire flock of wild parrots sitting in the trees over their.

Answer 1

The sentence that shows the correct use of a common homophone is:

They’re still not finished with the project that was due yesterday.

In this sentence, "they're" is correctly used as a contraction for "they are."