Final answer:
The smart dimension tool in CAD software automatically adds a radius or diameter dimension to an arc, depending on the context and tool settings.
Step-by-step explanation:
When you select an arc using the smart dimension tool in CAD software, it automatically adds a radius dimension or diameter dimension. The software determines whether to add a radius or diameter dimension based on the context of the arc within the drawing and the settings of the smart dimension tool. If you're working on a smaller arc or a part detail that represents a partial circle, the smart dimension tool typically applies a radius dimension. However, if the arc represents a full circle or a major portion of it, a diameter dimension may be assigned. The goal is to provide the most useful and clear information for whoever will be interpreting the drawing.