The evidence and explanation that best show how the historical setting contributes to the effect of personification in the passage is:
"and in the drone of the aeroplane the voice of the summer sky murmured its fierce soul."
This line personifies the "summer sky" by giving it a "voice" and characterizing it as having a "fierce soul." The historical context of the era, during which airplanes were becoming more prevalent, contributes to this personification by blending technological advancement with the natural environment. The mention of the "drone" of the airplane adds a layer of modernity that contrasts with the tranquil and idyllic setting of Kew Gardens. This juxtaposition enhances the personification, as it suggests a dynamic interplay between nature and the disruptive presence of technology, thus creating a vivid atmosphere that reflects the historical period's themes of change and modernity.