1. The problem asks which graph represents a function that is periodic and sinusoidal. 2. A periodic function repeats its values in regular intervals or periods. 3. A sinusoidal function is a smooth, wave-like function that can be represented by sine or cosine functions. 4. Among the options: - (A) is a parabola, which is not periodic. - (B) is a vertical wavy pattern but not a standard sinusoidal shape. - (C) is a sinusoidal wave, matching the sine or cosine function shape. - (D) is a wave with sharp peaks, not sinusoidal. 5. Therefore, the graph in option (C) represents a function that is periodic and sinusoidal. Final answer: (C)