The poet's purpose in writing the following lines, "That you with music, I with light, Might beautify and cheer the night" is (C) to show the two creatures as being part of the same world and working together. The poet is suggesting that both the nightingale, with its beautiful music, and the glow-worm, with its gentle light, have a role to play in making the night beautiful and cheerful. By bringing together two different creatures, one that produces light and one that produces sound, the poet is emphasizing the idea that all creatures have their unique gifts and can contribute to the world in their way. The lines highlight the interdependence of different species and the importance of each creature's role in the larger ecosystem.