Which is the most effective way to combine sentences 5 and 6?
He started a new league called the All-American Girls Professional Baseball League (AAGPBL).
The All-American Girls Professional Baseball League (AAGPBL) was the new league he started.
The All-American Girls Professional Baseball League (AAGPBL), a new league, started by him.
He started a new league, and it was the All-American Girls Professional Baseball League (AAGPBL).