Final answer:
The correct preterite form of the verb (traer) for the subject 'Ellos' is 'trajeron'.
Step-by-step explanation:
The correct preterite form of the verb (traer) for the subject 'Ellos' is 'trajeron'. So, the sentence would be: 'Ellos trajeron el helado a la mesa.'
Learn more about preterite form of the verb 'traer'