We recommend that you rotate (alternate) every other year between TruthBook B and C. 

Between TruthBook B and C are the 120 Q&A that are covered within levels 2-4.  Therefore, by alternating between the two TruthBooks you will cover all 120 Questions/Answers within the Discoverers years.  If you have a younger child in the program (3 year old), feel free to circle the 1-2 answers (or shorten answers) you want him/her to memorize (don't expect as much out of a 3 year old as you do a 4 or 5 year old.