instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Models may be physical, conceptual, or mathematical. Answer: mathematical
answer:
Models may be physical, conceptual, or what else?

question:
Passage: Bacteria are responsible for many types of diseases in humans. Answer: diseases
answer:
Bacteria are responsible for many types of what in humans?

question:
Passage: Covalent compounds form individual molecules rather than crystals. Compared with ionic compounds, they have low melting and boiling points. They are also poor conductors of electricity. In polar covalent compounds, oppositely charged ends of different molecules attract each other. This affects the properties of polar compounds. Answer: crystals
answer:
Covalent compounds form individual molecules rather than what?