What characterizes a cul-de-sac?

A cul-de-sac is characterized primarily as a dead end road, which is why the correct answer is identified as such. This type of street typically has only one entrance and exit point, leading to a circular turnaround at the end. Cul-de-sacs are often found in residential areas where they provide access to homes without allowing through traffic, thereby enhancing the safety and quietness of the neighborhood.

In contrast, the other options describe different road features. Roads that connect to a major highway facilitate major traffic flow and are designed for through movement, which is fundamentally different from the restrictive nature of a cul-de-sac. A roundabout, while it may have circular features, includes multiple exits for the continuous flow of traffic, which does not align with the concept of a cul-de-sac being a single, enclosed street. Lastly, one-way streets allow traffic to flow in a single direction but can connect to other streets or roads, unlike a cul-de-sac that ends with no further outlet.