Add the missing subject or predicate to create a complex sentence. ______ was found in the old barn.

The missing subject is "A treasure". The complete sentence is "A treasure was found in the old barn."

To create a complex sentence, you can add a subject or predicate to the sentence "______ was found in the old barn." Let's add a subject to make it a complex sentence:

"The lost treasure ______ was found in the old barn."

In this sentence, "The lost treasure" is the subject that has been added, making the sentence more complex.

The cat ______ was found in the old barn.