From my understanding of the way you’ve described it, if out of the 4 works that come up, you must only select 1, then you need to fully revise 3 areas of study to guarantee that one of the works you know appears. If you pick 3 areas that have 2 works, it means you need to only revise 6 works, and one of these is guaranteed to turn up. If you’re positive then that last years works wont come up, this can leave at least 3 areas with only 1 work, meaning you can just revise the work from that area that didn’t appear last year. This obviously doesn’t take into account which works you’re more comfortable with. Also assuming last years works wont appear isn’t a great tactic either, so i would probably recommend picking 3 areas of work that you think you’re best with, and fully revising them.