The old man has________ useful horse and ????????? horse can do a lot of things for him.

A. an; aB. the; a C. an; the??????? D. a; the

---Why not take ____ umbrella with the sign “Made in China”? It’s ____ useful one.
--- What ____ good advice.

-- Who is ____man in a black hat?
-- It’s Jim Black. We often play _______ baseball together in our free time.