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. It's snot easy to find a reader this entertaining! Learn about mucus in humans and animals, and even in the laws of our countries! Use the unique code inside the book to access the online reader, complete with videos and interactive exercises. Word count: 1727. Lexile Reading Level: 640L.