The correct answer is D) purple line. On a weather map, an occluded front is represented by a purple line. This is because an occluded front is a combination of a warm front and a cold front, where the cold air has caught up to and undercut the warm air mass. The purple color is used to distinguish this unique frontal system from the standard blue (cold front) and red (warm front) lines. The other options are incorrect because they do not accurately depict the visual representation of an occluded front on a weather map. A blue line represents a cold front, a dashed blue line indicates a stationary front, and an alternating red and blue line denotes a warm front.