Final answer:
The three categories mentioned - noninvasive & simple, noninvasive & complex, and invasive & complex - are classifications of diagnostic tests in the field of medicine.
Step-by-step explanation:
The three categories mentioned, 1. noninvasive & simple, 2. noninvasive & complex, and 3. invasive & complex, are classifications of diagnostic tests in the field of medicine. These categories represent different types of medical imaging techniques used for diagnosing and monitoring various conditions. Noninvasive tests do not involve any penetration of the body, while invasive tests require the insertion of instruments or substances into the body.