answer: #Person1# and #Person2# are discussing various purposes people use dogs for. #Person1# mentions horses are still used to pull plows and carts, and #Person2# suggests that they go horse riding together at the weekend.
documents: #Person1#: I was just watching a documentary on tv about people use dogs for various purpose. It was very interesting.
  #Person2#: I love dogs. They have been used as guards for centuries. Nowadays, they are often used to find illegal drugs and bombs by the police and customs officers.
  #Person1#: The documentary also pointed out that they are used by shepherds to round up sheep and by rescue workers to find people trapped under rubble or snow.
  #Person2#: Horses are useful to people too. We use them for sports and recreation.
  #Person1#: Don't forget that horses are still used in many countries to pull ploughs and carts.
  #Person2#: Can you ride a horse?
  #Person1#: Yes, I can. I don't ride regularly though. How about you?
  #Person2#: I can ride too. Perhaps we could go horse riding together at the weekend?
  #Person1#: What a good idea!