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

Example Input: Urea and carbon dioxide are molecules with how many carbon atoms?
Example Output: one

Example Input: Strong, stable bonds between carbon atoms produce complex molecules containing chains, branches, and rings; the chemistry of these compounds is called what?
Example Output: organic chemistry

Example Input: Osteoporosis, osteoarthritis, fractures, and sprains are problems affecting what system?
Example Output:
skeletal system