The correct answer is B) perfect visibility conditions, limited only by the curvature of the Earth. The geographic range of a light is the maximum distance at which it can be seen under ideal visibility conditions, which is limited only by the curvature of the Earth. This is because the Earth's curvature, rather than atmospheric conditions or the intensity of the light, becomes the limiting factor in how far the light can be seen. The other options are incorrect because they either introduce additional limiting factors (like visibility conditions or background lighting) or do not accurately describe the geographic range as being limited by the Earth's curvature.