Respuesta :
Answer:
4. Peaceful, I also had this same question and I sure you this is the answer
Explanation:
I would say 4. peaceful, because he is talking about how birds fly with "no perceptible exertion beyond that required to balnce and steer themselfs" and it not complaining about how humans can't do that
this could be wrong this could be right, but this is the best choice in my opinion, I know this is late but for the people who need it, here it is. :)