What do yellow-green signs indicate?

Answer: C — Warning

Yellow-green signs primarily serve to provide warnings, particularly related to pedestrian and bicycle-related areas. These signs alert drivers to the presence of pedestrians, school zones, and other areas where caution is necessary due to potential hazards associated with non-motorized travelers. The distinctive color combination is chosen specifically to attract attention and convey the urgency of the situation, ensuring that drivers are aware of their surroundings and can take appropriate action. The other categories—regulatory signs are typically regulatory in nature, enforcing laws and regulations; informational signs provide directions and general information; guide signs are meant to help travelers navigate roadways and find services—do not apply here since the yellow-green color is explicitly designated for warning purposes.