__________ is an effort or strategy to achieve a goal or a solution to a problem that is not readily apparent.

Problem solving is the effort or strategy used to reach a goal or find a solution when the answer is not readily apparent. A schema is an organized mental framework, a transformation problem is a type of problem involving a change from an initial to a goal state, and a prototype is a typical example of a category. Therefore, the best answer is A, Problem solving.

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