hi amour, think of some basic idea where someone transitions from not belonging to belonigng, just because you don't want to blank out on the day!
I memorised one for the trial but the question was so specific I did wing it... I kind of use the same character in all my practice ones so I don't have to think of one on the spot, but the scenario and plot was just invented on the spot (I did the same thing for extension 1). The teacher said I used the stimulus really well, so if anything, make sure you incorporate it in a solid way! That's the advantage you have if you do wing it. Some ideas in my story came out of my own life and a woman I saw in a documentary years ago who I found really memorable, and I think this made it easier to write.
Anyway you can wing it and do well if you figure out a loose plot as you read the question. I'd memorise some nice language though, and slip it in wherever you can. Also balance description with dialogue (some teachers hate it when there's no dialogue at all)... but then some teachers don't mind. It's so subjective!