The correct answer is "right curve ahead" because it accurately describes a road that is curving to the right. This warning sign is commonly used to alert drivers of a sharp or gradual curve in the road that they need to navigate. The other options, such as "right turn ahead" or "merging traffic to the right," do not accurately describe a curve in the road. "Winding road ahead" could be a possible alternative, but "right curve ahead" is a more specific and precise description.