Each load looks as if it contained the contents of a dozen shanties, and if one shanty so poor, this is a dozen times as poor
In this sentence, what figurative device does Thoreau use to establish the tone of this passage more strongly?

the best option is B) A book about bald eagle nesting sites in the United State.  

Explanation:

Of all the options cited above, the most authoritative source would be a book.

The next best resource is a website about bald eagle counts, as long as the information on the website is also acquired credibly and is a true research work not some copy and paste work.

Journals are also fine, whilst magazines would be the least resort.

Cheers!