The tone of the passage is loving (B).
The author is bragging about his or her little sister. The author is very proud of her and everything that she has accomplished. There is no part of the passage that would suggest that the author is angry with his or her sister, critical of her, or envious of her. The passage simply is stating the little sister's accomplishments.
"Please talk quietly in the library."
Imperative because it gives a command or request.
Hope I was able to help! :)
