Which One Doesn't Belong?

Winner of the 2017 Mathical Book Prize. Every colourful page of Christopher Danielson's children picture book, Which One Doesn't Belong. contains a thoughtfully designed set of four shapes. Each of the shapes can be a correct answer to the question "Which one doesn't belong. ” Because all their answers are right answers, students naturally shift their focus to justifications and arguments based on the shapes' geometric properties.