Given a scientific question, generate a correct answer to it.

Input: Consider Input: The four major classes of biological macromolecules include carbohydrates, lipids, proteins, and what else?

Output: nucleic acids

Input: Consider Input: What are insect parasites transmitted sexually?

Output: pubic lice

Input: Consider Input: What title is used to describe health professionals who use nonsurgical techniques to help patients with musculoskeletal system problems that involve the bones, muscles, ligaments, tendons, or nervous system?
Output: chiropractor chiropractors