Nowadays, alomost every family has a dog or a cat as a pet.Because the can bring us happinese.When we have something uahappy and don't want to tell anyone else,we can always talk with our pets,though perhaps they don't understand at all.But if we do so ,we will fell much better,especially when we're alone.When adults are busy and have no time to look after their parents.A pet will always a best present to the olds.But,keeping a pet will also bring us quite a lot trouble.For example,most pets are very dirty and they have a lot of diseases with them which will make us ill.Sometimes a dog will bite someone who may just want to touch it to express his friendship.In this way pets will also make people unhappy!