A yellow sign is commonly understood to indicate what?

Answer: C — Warnings

A yellow sign serves as a warning to drivers about potential hazards or changes in road conditions ahead. This color is used universally to capture attention and alert drivers to exercise caution. For example, a yellow sign might indicate merging traffic, a curve in the road, or a pedestrian crossing. These signs are essential for enhancing safety by communicating important information that can help drivers prepare for what lies ahead. In contrast, other colors have specific meanings. For instance, regulatory signs often use red or white to convey laws and commands that must be followed, such as stop signs or speed limits. Directional signs predominantly utilize green and blue to guide drivers toward destinations or indicate services. Construction zone signs usually have orange to signify work areas. Thus, yellow uniquely signifies caution and the need for alertness, making it distinct from the interpretations associated with the other colors of signs.