instruction:
Given a scientific question, generate a correct answer to it.
question:
What model postulates that electrons orbit the nucleus at fixed energy levels?
answer:
bohr

question:
Which part of the body has mucus and hair to trap dust and also warms and moistens air so to not harm lung tissue?
answer:
the nose

question:
Did the the open circulatory systems of molluscs and arthropods arise dependently or independently of each other?
answer:
independently