Answer:
I would say the best answer that fits here is El verano pasado
Step-by-step explanation:
Let me explain by translating all the other options and see which ones match up best
Anteanoche means the night before last
Anteayer means the day before yesterday
La semana pasada means last week
and finally, El verano pasado means last summer
Its not specific when he lived with his aunt but the one that makes the most sense is El verano pasado
**Viví con mí tía durante dos meses means I lived with my aunts for two months