Animals are our friends. We can find different kinds of animals on Earth. Some animals are living in big forests. And some animals are living with man. Animals are very important to man. For example, people can train the elephants to do some heavy work. And they can also train the dogs to look after the house. A police dog is clever. It can help people in danger. And it can also help the policeman to catch the thieves or murderers. The children like dogs very much. Everyone knows sheep and pigs very well. Man eats their meat almost every day. People can make coasts and shoes with their skins. From cows, we can get milk. It's good for our health. And horses can take us to other places. In some places, horses and camels are instead of car and buses. It's clear that man can't live comfortably without these animals. We can get milk from  _  .
dogs pigs hens cows