Answer:
The revision that uses an appositive to combine the sentences is the following one: Mr. Turner, my American history teacher, taught us about the U.S. home front during WWII.
Step-by-step explanation:
An appositive is a noun or noun phrase that renames another noun right beside it. Those appositive phrases which are considered nonessential are separated from the rest of the sentence with commas.
In the sentence above, the appositive phrase is the NP "my American history teacher". This NP renames the proper noun Mr. Turner. As you can see, this nonessential appositive phrase has been separated from the rest of the sentence with commas. If it was dropped, the meaning of the sentence would be left unchanged.