Answer:
Then in a wailful choir the small gnats mourn
Among the river sallows, borne aloft
Or sinking as the light wind lives or dies;
Step-by-step explanation:
The passage includes clues the word "choir" which has to do with music, therefore it's describing the gnats mourn as a wailful choir being autumn's music.
Also, it's the correct on the edmentum quiz bcz I just took it :)