I can see how the answer to K is sci-fi, but I'd definitely place Harry Potter in the fantasy category.
Of course, sci-fi does tend to overlap with horror, fantasy and action fairly often.
Scifi&fantasy are often put into the same category in bookstores, movie rental etc. so for some it is easier to just label both of them under SCIFI. And for some Scifi/fantasy also includes everything that "isn't happening in a world identical to ours" OR has anything supernatural OR has any technology not available in real life. (So by that categorization even knight rider is scifi. )
This is a rather wide categorization, especially if you like to separate the subgenres in scifi and fantasy. (high fantasy, low fantasy, steampunk, cyberpunk, etc.punk, magical-reality...) Personally I am rather annoyed at the huge amount of different genre-specifications. "Magical-reality is set in a very real like world and only has few examples of magic or other supernatural things."
But is it really so different that it needs a separate genre from fantasy? Bah!
At least the creators of "trollpunk" did it as a joke.
(Few writers and reporters annoyed about all these new genres popping up, mostly just because no one wanted to be labeled as a "fantasy-writer" so they decided to troll people by creating a new genre, apply named "trollpunk" which is set in a world which is otherwise "normal" but has trolls. First some of them wrote some articles where they offhand mentioned the genre then Johanna Sinisalo wrote the first "trollpunk-book" and then the term got loose... Some other writers and reporters began to use the term and actually expanded upon it because they did not realise that it is a joke.)
Sorry about ranting. Again...