Final answer:
The appropriate preterite verb to fill in the blank is 'se divirtió'.
Step-by-step explanation:
In the given sentence, the appropriate verb to fill in the blank is se divirtió. This is because the subject 'Nadia' (third person) is the one who had fun at the beach. The correct conjugation of the verb 'divertirse' (to have fun) in the preterite tense for the third person singular is 'se divirtió'.
Learn more about Conjugation of the verb 'divertirse' in the preterite tense