Hey!

Even if you know a bit about the question being asked in the exam, do try to write it up because if not full marks, you will certainly get some marks even if it's a half. So, it's better than nothing. Try to frame your answer in such a manner that it somehow answers the question even if it's incomplete. Don't write just anything but something that you are sure of is correct and is relevant to the question being asked. It is because if you write just anything random, it would not fetch you any marks and it will ruin the time which you otherwise would have utilised while writing another answer.

Write something related to it :)