They may either specify the form/type of writing to use, or they may allow you to choose between persuasive, discursive and imaginative.
Consider the relevant 2020 Paper 2 question:
"Compose a piece of imaginative writing that begins with the words"
Consider the relevant 2019 Paper 2 question (part a):
"Continue this extract as a piece of imaginative, discursive or persuasive writing that evokes a particular emotional response in the reader."
It would be a good idea to ensure you have sufficiently practised writing using each form just to be safe.
I hope this helps!