Which sentence is the correctly written simple sentence?
 A.
 Gettysburg is one Civil War battlefield Antietam is another.
 B.
 Gettysburg and Antietam are both Civil War battlefields, and I have toured them both.
 C.
 Gettysburg and Antietam are Civil War battlefields.
 D.
 Gettysburg is a Civil War battlefield and so is Antietam.