Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 22 to 29.

Many people have dogs for pets, but did you know that the dog was the first animal to be domesticated? That means it was the first animal ___(1)___ was kept and cared for by humans. Dogs have been kept as workers, hunters, and friends for much of human history.
Dogs were originally gray wolves, but domestication gradually ___(2)___ this. Humans have selectively bred dogs for traits that they believed were good. That's how many varieties of dogs came to exist today.
Dogs come in all ___(3)___ and sizes. Dogs also have different kinds of coats. Some of them have long hair, while others have short. This hair can come in ___(4)___ different colors and patterns. Dogs also have different skills. Some varieties are good at hunting wild animals, while others are good at herding cattle or ___(5)___ people.
Because dogs are closely related ___(6)___ wolves, it might seem like they would be violent. ___(7)___ some dogs are violent, 15,000 years of domestication has made most dogs friendly to human. Today's dogs are much easier to train than wild wolves. They respond well to human training: learning to sit, roll over, and even ___(8)___ dog shows. Training dogs is a practice that has been improved for many, many years.