An AI is using a step-level search tree to solve a complex problem. In this tree, a 'terminal node' represents the end of a complete reasoning path. A path is considered complete if it solves the problem or if no further valid steps can be taken. Analyze the descriptions of four nodes reached by the AI. Which node represents a terminal state that is also a valid solution to the problem?

Evaluating Reasoning Paths in a Search Tree

In a problem-solving process that uses a search tree where each path represents a sequence of reasoning steps, every terminal node (a point where a path ends) necessarily corresponds to a correct and optimal solution.