Which is NOT a controlling idea in the essay?

The correct answer is D: Fräbel-designed crystal peach.

Explanation: A controlling idea in an essay sets the direction or focus of the writing. Options A (average joggers), B (importance of tradition), and C (Olympic-level competitors) all suggest broader themes or subjects that could guide an essay. In contrast, D refers to a specific object (the crystal peach) rather than a general concept or idea, making it not a controlling idea for an essay.