Final answer:
The appropriate form of the verb estar to fill in the blank in the given sentence is 'estás'.
Step-by-step explanation:
The appropriate form of the verb estar to fill in the blank in the given sentence is option B. estás. The sentence is asking 'You are in English class with Juan, aren't you?' and the subject 'tú' (you) requires the form 'estás' (are). The other options are incorrect because 'estamos' is the form for 'nosotros' (we), 'eres' is the form for 'tú' (you) with the verb 'ser' (to be), and 'estoy' is the form for 'yo' (I).
Learn more about Spanish verb conjugation