The essential criteria that Oxford is looking for is intellectual curiosity and how you use this to explore a topic/question/statement. Therefore, you should be prepared to answer in a way that demonstrates understanding of both sides of an argument, possibly coming to a conclusion but being analytical along the way. Given the short amount of time, try to be concise in your ideas and don't just focus on one idea, add many points that have been briefly considered to sway the argument in one direction or even come to an answer that is neutral, perhaps even challenging the question. Given the demands for such little time, planning is essential so it's worth spending five minutes on this at the start. Lastly, you don't even need to answer the economics focused one, I wrote about religion! The topic is less important than how you write the answer.