【单选题】读下面等高线地形图，回答问题。 图中表示鞍部的是（     ） A．A    B．B    C．C    D．D---**Chart Description:** * **Type:** Topographic map or contour diagram. * **Main Elements:** * **Contour Lines:** Multiple irregular closed loops representing different elevations. The visible elevation values are 100, 300, and 500, increasing towards the centers of the closed loops. The outermost visible contour line is the lowest (implied or 100), and the innermost closed loops are the highest (above 500). * **Points/Areas:** * Point A: Located within a smaller, innermost closed contour line on the left side of the diagram. There is a small triangle symbol pointing upwards within the contour surrounding A. * Area C: Located between the contour surrounding A and the main elevated area on the right. * Area D: Located to the south of Area C, along a contour line. * Point B: Located outside the main contoured area, to the southeast. * Line/Area E: A vertical line segment on the far left, with short horizontal segments extending to the right, representing a feature like a cliff or wall. It is located outside the contour lines. * **Numbered Lines:** Four lines with arrows pointing towards the central elevated area on the right: * Line 1: A diagonal line from the top, pointing southwest towards the central elevated area. * Line 2: A diagonal line from the northeast, pointing southwest towards the central elevated area. * Line 3: A horizontal line from the east, pointing west towards the central elevated area. * Line 4: A diagonal line from the southeast, pointing northwest towards the central elevated area. * **Compass Rose:** An arrow labeled "N" pointing towards the upper right, indicating the direction of North. * **Symbols:** A small triangle pointing upwards in the center of the contours around A and within the innermost contours of the central elevated area on the right, likely indicating peaks. **Extracted Textual Information:** * Labels: A, B, C, D, E, N, 1, 2, 3, 4 * Contour Values: 100, 300, 500 **Other Relevant Text:** * (No other explicit text like question stems, options, hints, or titles is present in the image.)