Answer:
Fui
Step-by-step explanation:
El año pasado means last year, so we have to pick a choice in the past tense.
Voy and vas are in the present tense, so they are not correct.
Fui and fuiste are both in the past tense. The sentence uses yo, so fui must be the correct choice.
El año pasado yo fui a Maine de vacaciones.
Translation: Last year, I went to Maine on vacation.