What does a blue circular sign indicate on the road?

Answer: B — No turns are allowed

A blue circular sign on the road specifically indicates that it is a designated parking area. These signs are commonly used to indicate that parking is available for certain types of vehicles, including those with disabilities. The blue color helps to distinguish these parking spots from others, making it clear to drivers that they can find suitable places to park. The other options refer to instructions or prohibitions related to turns, which are typically indicated by other shapes and colors. For example, no turns would typically be indicated by a sign with a different color and shape, such as red and white. In contrast, the blue circular sign is consistently used to convey information about parking zones rather than directional instructions.