The "D1" designation refers to the . It typically contains 200 worksheets, each designed to take 10–15 minutes to complete.
If answer books were readily available online, the integrity of the program would collapse. Students would simply copy answers to get through the worksheets quickly (a practice Kumon students call "speed-running"). This defeats the purpose of the "Self-Learning" philosophy that Kumon is built upon. Kumon D1 Answer Book English