Final answer:
The preterite tense is used to indicate an action that happened and was completed in the past.
Step-by-step explanation:
In the preterite tense, the sentence 'Tomás fue a visitar a sus abuelos el año pasado' translates to 'Tomás went to visit his grandparents last year.' The preterite tense is used to indicate an action that happened and was completed in the past. In this sentence, 'Tomás' is the subject and 'fue' is the verb in the preterite tense. The phrase 'el año pasado' specifies the timeframe of the action.
Learn more about Preterite tense in Spanish