It may seem as though you are unable to revise for this section of the exam as you do not know what the questions will be, but there is in fact a lot you can do to prepare. My advice would be to write vocabulary lists of alll the topic relavant vocabulary you have learnt throughout the year, by looking at your class notes and text books. Memorise these words as they will come in very handy. It is also useful to ahve a rather firm grip on the basic grammar principles, so I reccommend revising your tenses, by memorising the verb endings and conjucations.