Final answer:
The correct answer is 'Vas'.
Step-by-step explanation:
The subject of this question is Spanish. The question is asking for the correct form of the verb 'to do' in the sentence 'What are you going to do tomorrow?' The options given are 'Va', 'Vas', 'Voy', and 'Vamos'. To correctly match the subject of the sentence, we need to use the pronoun 'tú' for 'you'. In Spanish, 'tú' corresponds with the form 'vas'. So the correct answer is B. Vas.
Learn more about Spanish verb conjugation