I have described myself as always having been imbued with a
fervent longing to penetrate the secrets of nature.
In this line, the author is exploring man versus nature. The
word or phrase from this passage that best demonstrated the conflict between
man and nature is perhaps ‘penetrate’ or specifically ‘penetrate the secrets of
nature’.
‘Penetrate’ means to succeed in forcing a way into or
through. This signifies that the persona in this passage wants to understand
the mysteries that surround nature.
I would say D, since A and B would be highly irrelevant. C sounds like a possible answer, but could still be viewed as irrelevant since it doesn't actually contain info about MP3 players.