The background noise in the radio programs serves to the listener as a way to identify the place where the events hapens. Sounds proper of the eviroment such as animals noises, other people talking, cars, waves in the ocean or other climate indicators. It provides them with a context that helps to better understand what is going on.
90% sure it's D. And I have to make this answer long or else I can't submit it so that's why I added this whole sentence
Paired conjunctions
Either......or
Neither......nor
Not only.....but
Iwill go either to Rio or Bahia on my vacation
Neither John nor Mary speaks French
Not only does he speak French,but also German
I would say it is answer A as the tone of the poem is very joyful
