REA's CLEP Natural Sciences Test Prep Earns You College Credits! New from REA - CLEP Natural Sciences! The latest addition to REA's CLEP library! If you're looking for an easy way to earn college credit, why not take the CLEP Natural Sciences exam? Written by experienced science teachers, REA's CLEP Natural Sciences test prep features an in-depth review of Biological Science and Physical Science. It covers all the topics found on the official CLEP exam, such as: origin and evolution of life, cell organization, atomic and nuclear structure and properties, chemical elements, the universe, and more!- from product description.