Which revision of the sentence is now properly punctuated? Theodore Roosevelt, the twenty-sixth president of the United States, was the youngest president to ever hold office.
Theodore Roosevelt the twenty-sixth president (of the United States) was the youngest president to ever hold office.
Theodore Roosevelt the twenty—sixth president of the United States—was the youngest president to ever hold office.
Theodore Roosevelt, the twenty-sixth president of the United States was the youngest president to ever hold office.