Final answer:
The sentence should be completed with the correct form of the verb 'estar', which is 'está' in this case. 'Mi hermano está detrás del carro.'
Step-by-step explanation:
The sentence should be completed with the correct form of the verb estar, which means 'to be' in English. The subject 'mi hermano' indicates that the verb should agree with the third person singular. 'Detrás del carro' means 'behind the car'. Therefore, the correct form of 'estar' is está.
Learn more about Verb conjugation in Spanish