One of the vaguest topics I've heard of, but I guess that's good cause you have lots of room for interpretation. I'm currently doing Energy, power and dynamism for my as exam and it's a pretty good match cause I like doing expressive stuff and the topic is pretty broad as well.
Truth, fantasy and fiction seems trickier as truth and fantasy are polar opposites so perhaps implementing some double meanings into your work might be a good idea. Considering you're doing A2 I'm sure you've heard this advice but It will probably be a good idea to stick to your favourite style of art, e.g. I like to draw or paint land/street scapes in an illustrative but detailed fashion so when I had to do responses to Stanley Donwood's linoprints, I took pictures of streets, drew them out in as much detail as possible and incorporated elements of his work, namely wiggly lines on the streets to indicate flooding as well as meteors coming down from the sky. So, basically, if there is a way to do a response to an artist whilst not steering away from your style, you shuold do that, instead of forcing the style of the artist onto yourself.
You might wanna make up the vague big picture of your final piece now, so your sketchbook doesn't beet around the bush 2 much but of course don't limit yourself to it and alter it when you find other, more suitable stuff. I remember doing several 180s in my coursework, but I'm keeping it more real this time with a clearer general premis to all of my responses and other stuff.
If, like me, you like doing landscapes, I guess stuff like this might be suitable:
Other than that I heard the name of Jenny Saville around this topic a lot. I guess her paintings have connotations to the theme, e.g. one of her paintings is a man with a vagina which I guess might link into it, but it's quite the roundabout. Also, I guess sexual fantasy might be a good groundwork but keep it lowkey. Other than that, I'd encourage you to look at Beksinski's work. You will find some imgur albums of his stuff and it might give you some ideas, it kind of sucks that I can't use him as inspiration for my topic, because it's fiction-based stuff that can be extended into anything you want, really. With that said, I'd guess your teacher already gave you some artists to look at based on your style and preferences. I don't know if any of this helps, it's just things that I'm thinking.