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

Example Input: What is added to alcohol and used as an antiseptic?
Example Output: iodine

Example Input: The four major classes of biological macromolecules include carbohydrates, lipids, proteins, and what else?
Example Output: nucleic acids

Example Input: What kind of lines does a diffraction grating produce?
Example Output:
evenly spaced lines