Final answer:
The subject of the sentence is 'este verano' and the correct form of 'ir' is 'voy'.
Step-by-step explanation:
The sentence is asking which form of the verb 'ir' (to go) should be used in the blank. The subject of the sentence is 'este verano' (this summer). Since the sentence is in the first person, the correct form of 'ir' is 'voy'.
Learn more about Spanish verb conjugation