Answer:
c. a concrete operational thinker.
Explanation:
Marty is most likely a concrete operational thinker. Concrete thinking is the third stage in Piaget's theory of cognitive development. It is characterized by logical thinking of real life situation and how to solve those situations Marty is faced with a real life situation on how to locate the center of equilibrium of the board with the changing load. Solving and managing such real life situation is a characteristic of a concrete operational thinker.