Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word for each of the questions from 39 to 43.

     Dogs originally came from wolves. Wolves look a lot like dogs, but they are bigger. They are also quite fierce. At some point, some wolves changed through evolution. Some of them were smaller and gentler. These nicer wolves were the first dogs. No one knows for sure when this happened or why. Some people say it happened naturally over 50,000 years ago. Others say people made it happen between 15,000 and 50,000 years ago. 

     However they came to be, people quickly saw that dogs were useful. Scientists who study humans say the first tame dogs appeared with humans about 13,000 years ago in the Middle East. Not long after, there were dogs in Asia, Africa, Europe and eventually, North America. These dogs were probably used mostly for hunting and traveling. They were also good companions. 

     Dogs were an important part of life in ancient Egypt. Egyptian dogs were used not only for hunting, but as guards and warriors as well. They believed the god that guarded hell was a dog. Ancient Egyptians also named their pet dogs. Some popular names meant Brave One, Reliable, North-wind, Blacky, and Useless. 

     Dogs were also good ancient Roman warriors. The Roman army used dogs all over Europe. Sometimes the dogs were attack dogs, but her times the dogs were messengers. 

     There are many different kinds of dogs today. How could they all come from wolves? There are many different explanations. Some scientists believe that dogs mixed with other animals from the Canidae family. This includes coyotes, foxes and jackals. Most scientists also believe that evolution and breeding influenced the variation. Later, people found breeds of dogs they liked and combined them to make all new breeds. In this way, people are still helping new breeds to appear today! 

Which of the following best states the main idea of the reading?