Final answer:
The correct word for the sentence is 'Tiene'. Usted is the subject pronoun for 'you' formal in Spanish, and 'tiene' is the third person singular form of the verb 'tener' which means 'to have'.
Step-by-step explanation:
The correct word for the sentence is Tiene. Usted is the subject pronoun for 'you' formal in Spanish, and 'tiene' is the third person singular form of the verb 'tener' which means 'to have'. So, the sentence should read 'Usted tiene un perro', which translates to 'You have a dog' in English.
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