I'll leave lilacwanda28 to have the last word; but generally speaking when a question is broad they want to hear from you directly about your own view. This question does what it says on the tin; it's asking you (as opposed to anyone else) how you could serve society if you get the prize to study at King's.
So work out how you could serve society using your own interests, passions, social concerns and choice of degree subject and why King's is the appropriate place to do that.
Would you agree lilacwanda28?