Concept:Problem-solving is improved by thinking that produces many different ideas and solutions, not by rigid or imitative thinking.Explanation:Divergent thinking means exploring many possible answers to a question. This open-ended approach encourages creativity and flexibility, which are essential for solving new problems.Passive imitation simply copies existing solutions and does not generate new ideas. Response set is a tendency to use the same method repeatedly, which can block fresh approaches. Functional fixedness limits thinking to the usual use of an object, preventing creative solutions.Only divergent thinking actively fosters the generation of varied and original ideas, making it the key factor that promotes problem-solving.Answer:C. Divergent thinking