Final answer:
The correct word to complete the conversation is 'anteayer', which means 'the day before yesterday'.
Step-by-step explanation:
The correct answer is A. anteayer. In the conversation, Pedro says that today is the 22nd of May. Fernando then concludes by saying, 'Entonces,' which means 'So,' or 'Therefore.' Anteayer means 'the day before yesterday,' so the correct phrase to complete the conversation is 'Entonces, anteayer fue el 20 de mayo,' meaning 'So, the day before yesterday was the 20th of May.'
Learn more about Completing a conversation in Spanish