article: Sam is a middle school student. He can't see. So he has a special  friend -- a dog. Its name is Blackie. Blackie takes Sam to school every day. They get to school at 7:15. They are never late for school.
  After school, Blackie takes Sam to the bus stop. Sometimes they stop first for an ice-cream. Blackie likes it, too. Then they take the bus home.
  Blackie also helps Sam in the sports class. Blackie is funny and everyone likes him. But in the music class, Blackie can't sing.
  In the evening, Blackie is tired   but he is happy. He relaxes under Sam's chair. Then Sam and Blackie go to bed at the same time.
question: Who is Blackie?
options: A boy. A girl. A student. A dog.