You take a story and explain the entire thing with only a couple paragraphs, and you don't want to give away any special details that way a person can know a little about the book and want to read it. Like a "A dog and His Ball" is about a lost dog who doesn't have a family and finds an old ball to play with. You would put this on the back of a book and then people would be drawn to read this book. ( I just made something up so it may not make sense sorry.)
I'm not really sure I understand what you are asking, but I tried to answer the best I could, please let me know if this isn't what you meant.
A.) Dream memories and fall leaves are being compared in the simile.
It is A, a gloomy day. when u think of black clouds, its gloomy, almost like its going to rain. it cant be the sun is setting because when it sets, clouds are sort of pinkish.if the clouds are moving, that really has nothing to do with the sentance. i hope this answer has helped.
The inclusion of reputable sources and specific facts would best strengthen the author's main argument because it would offer factual proof instead of just the author's opinion on the matter.