I believe the example of a caravan would be D. a group of people who travel to trade goods.
hope this helps!
A relative pronoun usually introduces an adjective clause
1) based on “grove” and “nature” i would assume a variety animal calls
2) “sad thoughts” seem to refer to the “what man has made of man” as it seems the poet is upset that the link of nature and soul is mended in some way. this could be reference towards deforestation or other acts we have caused to destroy nature
