Final answer:
The correct verb form to complete the conversation is 'fui'
Step-by-step explanation:
In this conversation, the correct verb form that completes Alberto's response is 'C. fui'.
When responding to Fernando's question, Alberto is using the first person singular form (yo) of the verb 'ir' (to go) to talk about his own actions. In the past tense, the correct form of 'ir' would be 'fui'.
For example:
Fernando: ¿Qué hiciste la semana pasada? (What did you do last week?)
Alberto: La semana pasada, yo fui a la playa. (Last week, I went to the beach.)
Learn more about Verb form in Spanish conversation