A pet is an animal that【21】in your house. Over half the families in North America own pets. The most popular【22】are dogs, fish and birds. Rabbits, hamsters and turtles are also popular. Even some unpopular animals such as frogs, mice and snakes are pets. People first【23】to keep pets about 12,000 years ago. The first pet was a dog. The dog did not become a pet because people【24】it was cute. It became a pet because it was useful. People used the dog for many things. The dog warned people【25】danger so wild animals didn't attack people. It also ate left-over food. Later, dogs helped people take care【26】cows and sheep on farms. Cats did not【27】pets for a long time. When the Egyptians first started to grow grain, mice ate it. The Egyptians were【28】to tame cats. Today, people keep many【29】of pets. Animals such as canaries, parrots, mice and hamsters live in cages. They need people to bring them food and water and to keep their cages clean. Other animals, such as dogs and cats, need food and water, but they can take care of themselves【30】.They are good pets for people because they don't need much care. (41)