To determine the radius of the base of the cylinder, we typically need a visual diagram or more contextual information. Since I cannot see the diagram you're referring to, I can't provide a definitive answer. However, based on the provided options (2, 4, 15), if you have a diagram, you can look for indicators, such as markings or dimensions, that suggest the size of the base.
If you have any specific information from the diagram that you would like to share, please do so, and I'll be happy to help you interpret it!