My English supplementary book for third grade sounds like a comprehensive resource covering all language skills across its twelve chapters. The book likely provides a structured approach to learning grammar, vocabulary, reading comprehension, writing, and speaking for young learners. It may incorporate engaging activities, exercises, and examples tailored to the developmental stage of third graders. Additionally, the book probably offers opportunities for practice and reinforcement of essential language skills through a variety of exercises, making learning both effective and enjoyable for students. In summary, your book seems to be a valuable tool for enhancing English proficiency in third-grade students by offering a well-rounded curriculum that targets all aspects of language learning.