OCR 21st Century Biology B4 Revision Resources. The crib sheet is a mind map of things students need to know for B4. I print the keywords two sides per page and double sided so they all fit on one A4 page and students can write down definitions of all the keywords; they can then test each other. I cut the board game questions up on card; the question is at the top and the answer is in italics beneath the question. Students can use these how ever they want e.g. see how many their partner can answer in one minute, or play a board game like snakes and ladders and they get an extra roll of the dice for every question they get correct.