Answer:
The answer is "It describes the innocence of youth"
Step-by-step explanation:
The line "And as I was green and carefree, famous among the barns" portrays the author's youth days. The poem, in general, is quite melancholic. He starts describing his old good days, spending time in a nice landscape with apple trees and daisies on the green grass. In that particular line, he matches the adjective green (meaning he was young) with the rest of the poem's content, the landscape. Children don't have responsibilities and always see the best side of things, that's why the author says "green and carefree".