Pronoun: its
Referent: dog
Explanation: The pronoun "its" refers back to the noun "dog". It is clear that "its" refers to the dog because it is the only noun in the sentence that can possess a tail.
Here are some other examples of pronoun reference:
* She went to the store and bought a loaf of bread. (She refers to a female person previously mentioned in the context.)
* The car is red. It is parked in the garage. (It refers to the car.)
* John is a good friend. He always helps me when I need it. (He refers to John.)
Important note: Pronoun reference should be clear and unambiguous. Avoid using pronouns in a way that could cause confusion about their referent.