By Anthony D. Fredericks. Retina, iris, cornea, pupil—which one does not belong with the other three? On 73 reproducible handouts with several brainstretchers per page, students test their scientific knowledge by analyzing patterns, working out analogies, categorizing, sequencing, and sifting facts from errors. Topic areas: physical science, life science, and Earth and space science. Grades 4–6. Answer key.