Read the passage. [1] Activation in a brain region often involved in memory does not prove that a participant is remembering, because the same region may contribute to attention, prediction, or imagery. [2] The experiment observed activity in that region while participants viewed familiar scenes. [3] Participants later recognized most of the scenes. [4] A stronger design would compare memory demands while holding attention and imagery constant. Which labeled sentence states the limitation of inferring a specific mental process from regional activation alone?