¿Qué variable no se puede modificar una vez creada la campaña?

The correct answer is "La segmentación automática o personalizada" (Automatic or personalized segmentation). This setting is a fundamental structural variable that cannot be changed once a campaign is created because it dictates the core logic and learning method the algorithm uses to display ads. Modifying the segmentation type would fundamentally alter the campaign's nature and data history, requiring a new campaign to be created. In contrast, the daily budget, maximum CPC, and selected products are dynamic elements that can be adjusted in real-time to optimize campaign performance without redefining its core strategy.