Correct! The correct answer is "d. se permite". In this sentence, the phrase "no es una buena idea" implies that taking photos in the theater is not allowed or permitted. The verb "permitir" means "to permit" or "to allow", so "no se permite" means "it is not allowed". Therefore, the correct phrase is "no se permite sacar fotos en el teatro", which translates to "taking photos in the theater is not allowed".
