Most people have had a dog or wanted one as their companion (伙伴) at some time in their lives. If you are thinking of buying a dog, however, you should first decide what sort of companion you need and whether the dog is likely to be happy in the surroundings you can provide. Specialists’ advice is useful to help you choose the most suitable kind of dog. But in part the decision depends on common sense. Different dogs were originally developed to perform specific tasks. So, if you want a dog to protect you or your house, for example, you should choose the one that has the right size and characteristics. You must also be ready to devote a great deal of time to training the dog when it is young and give it the exercise it needs throughout its life, unless you live in the countryside and can let it run freely. Dogs are demanding pets. Cats love the house and so are satisfactory with their place where there is security, but a dog is loyal to its master and consequently wants him to show proof of his affection . The best time to buy a baby dog is when it is between 6 to 8 weeks old so that it can transfer its love for its mother to its master. If baby dogs have not established a relationship with the human being until they are over three months old, their strong relationship will always be with dogs. They are likely to be too shy when they are brought out into the world to become good pets.