In what scenario might a driver encounter a decreasing radius corner?

Answer: C — In sharp mountain roads

A decreasing radius corner is a turn where the curve becomes sharper as you progress through it. This type of corner is typically found in sharp mountain roads. As vehicles navigate these roads, the curvature can tighten unexpectedly, requiring drivers to reduce speed and carefully manage their steering to maintain control. In contrast, straight highways usually feature wide, steady paths without sharp turns. Roundabouts are designed to have constant radii or slightly increasing radii to facilitate smooth transitions. Similarly, traffic signals do not feature curves but rather direct traffic flow at intersections, making them unrelated to decreasing radius turns. Thus, the scenario of navigating sharp mountain roads is the most appropriate context for encountering decreasing radius corners, highlighting the need for heightened awareness and skilled driving techniques in such situations.