Final answer:
2-year-old Tommy’s expression of needing to use the bathroom after drinking water shows object permanence, which is the understanding that processes continue even when not directly observed.
Step-by-step explanation:
Tommy's statement, "go potty . . . drink water . . .," which he uses to express the need to use the bathroom after drinking water, best demonstrates object permanence. Object permanence is the understanding that objects continue to exist even if they are not currently being sensed.
In this context, Tommy's awareness that he needs to urinate after drinking water shows his understanding that processes (like digestion and the subsequent need for elimination) continue even when not directly observed. This concept is different from egocentrism, where a child cannot take the perspective of others; animism, attributing lifelike qualities to inanimate objects; or overregularization, which involves applying grammatical rules too generally.