註釋
Cambridge Discovery Education Interactive Readers are the next generation of graded readers - captivating topics, high-impact video, and interactive exercises designed to motivate and engage. Building a greener world! This reader explores the newest and cleverest ideas in sustainable energy and ecologically friendly construction. Use the unique code inside the book to access the online reader, complete with videos and interactive exercises. Word count: 2573. Lexile Reading Level: 880L. 
