Final answer:
The appropriate verb to fill in the blank is 'fueron.'
Step-by-step explanation:
In the sentence 'Ellas al supermercado anoche,' the appropriate verb to fill in the blank is D. fueron. This verb is the third person plural preterite form of the verb 'ir' which means 'to go.' So the complete sentence is 'Ellas fueron al supermercado anoche,' which translates to 'They went to the supermarket last night.'
Learn more about Verb conjugation in Spanish