Mermaids are a fiction topic. They were first introduced when Greek fishermen caught sight of dugongs, but mistook them for young maidens with the top half being human features, but the bottom half...
No. Realistic fiction indicates that the book is something that COULD happen, not that did happen. If there aren't talking animals or magic spells in it, for example, and it's a story about a kid...
Because sometimes the poet feels like expressing his humor. Sometimes the poet does not have humor, so he/she does not express it. I as a poet has humor, so I express my humor in most of my poems....
Counts as fiction. The fact that it is historical fiction just means that it is set in a time period that existed vs. other forms of fiction such as fantasy or scifi that exist in invented worlds.