1. A predicative nominative is a noun or a pronoun which follows a linking verb and refers to something before that verb. In your case, the correct answer is B, because "a shelter" goes after the linking verb "is", and refers to "a lean-to".
2. A participle has the form of infinitive + ing. In this case, the answer is D, flourishing.
Alloterations have repeated words that rhyme is untrue
Hope this helps and have a wonderful day :)
As someone who writes books, I'd normally use quotation marks, and the person is obviously talking, so the first one should be correct.
