Which of the following lines from john muir's "the calypso borealis" shows an example of dialect?
the flower was white and made the impression of the utmost simple purity like a snowflower.
no other bloom was near it, for the bog a short distance below the surface was still frozen, and the water was ice cold.
"i wish you would write me, say once a year, so i may keep you in sight."
"mony a puir body has been lost in that muckle, cauld, dreary bog and never been found."

Dialect is the particular form of language that is specific to a certain region or group of people. For example people in one region would say call soft drinks "Pop", but people in another region would call it "Soda".
So in the answer, we are looking for a form of speech. Now we can get rid of options A and B, because they have to forms of speech.
Option C has speech, but it has no slang, or peculiar wordsNow option D, however uses  the words "muckle, cauld" which aren't words used globally. They are dialects.
The answer is the last one, option D

He discusses the problem of human destruction of nature and gives solution to prevent it.