Final answer:
The shape of a stop sign is an eight-sided octagon, which is option a), and is designed for quick recognition by drivers.
Step-by-step explanation:
The shape of a stop sign is an octagon, which means it is an eight-sided polygon. Using the options provided, the correct answer to your question is a) Eight sided. Traffic signs often have shapes associated with specific meanings to aid in the quick recognition by drivers. While a diamond shape often indicates a warning, and a circle often indicates an impending order, such as a speed limit or no-entry sign, the octagonal shape is universally recognized to indicate a need to stop at intersections or road crossings.