Machines in Health is one of four books that make up the National Geographic Theme Set:: Using Simple Machines.  It is Book D.Each book in the set is written at a different reading standard, yet covers the same key concepts about the theme Using Simple Machines. This enables you to cater for all students in your class by teaching the same content to every student - from struggling to fluent readers - with books that cater for different reading needs.The goal of this set  is for all student