针对以上问题，生成动画讲解视频---**Extracted Content:** **Question Stem:** 4. (2016·春蕾杯) 如图, 整个圆分成了 A、B、C 三个部分, 且大圆直径被五等分, 求面积A : 面积B的比值. **Translation of Question Stem:** 4. (2016 Chunlei Cup) As shown in the figure, the entire circle is divided into three parts, A, B, and C, and the diameter of the large circle is divided into five equal parts. Find the ratio of Area A : Area B. **Chart/Diagram Description:** * **Type:** Geometric figure, specifically a circle divided into three regions. It resembles a simplified Taijitu (Yin-Yang symbol). * **Main Elements:** * **Overall Shape:** A large circular outline. * **Regions:** The circle is divided into three distinct regions, labeled A, B, and C. * **Region A:** Located in the upper-left part of the circle, unshaded. Its boundary includes part of the large circle's circumference and an S-shaped curve that forms the boundary with region B. * **Region B:** An S-shaped (or 'yin-yang' shaped) region spanning the horizontal center of the circle, shaded dark. It separates region A from region C. * **Region C:** Located in the lower-right part of the circle, unshaded. Its boundary includes part of the large circle's circumference and an S-shaped curve that forms the boundary with region B. * **Lines:** * A horizontal dashed line passes through the center of the circle, acting as a diameter. This line extends across the entire width of the circle and passes through region B. * Two small, solid black dots are positioned on this dashed diameter line, symmetrically located within region B, indicating points that divide the diameter. The problem statement clarifies that the "large circle diameter is divided into five equal parts," implying these dots (and potentially other implicit divisions) are part of that five-part division. * **Labels:** The regions are labeled "A", "B", and "C". * **Shading:** Region B is shaded dark, while regions A and C are unshaded (white).