I think creatives are the hardest part. You've got to write a relatively simple story because you have to fit it in 40 mins, so you can't exactly write a novel and all the pages to develop characters etc. But you also want it to be profound and not gimmicky.
But if you write about something too simple, say, a walk down the road to get a sausage roll, then you're screwed.
I've been told, or I'm under the impression that unless you're a brilliant writer, then you ought ot write something metaphorical.
Personally, I'd say write something that you yourself have experienced, or at least something you can write convicingly about.
ie. I doubt I could, in 40 mins, write convincingly about the experience of a WWI vet.
Go for something simple, and try make it a little personal, maybe even a little more personal, because then when you're writing, you can just let it all go.
Answering the question is always good....So if they ask you to use something as a basis, use it as a basis. If it's stimulus, like the CSSA paper, my teacher told me that the stimulus quote or something should be at the climax, or some profound time in your piece.
Hope it helps.