Given a scientific passage and an answer, generate a question for the given answer.

Input: Consider Input: Passage: An ionic bond is the force of attraction that holds together oppositely charged ions. Ionic bonds form crystals instead of molecules. Table salt contains ionic bonds. Answer: ionic bond

Output: What term means the force of attraction that holds together oppositely charged ions?

Input: Consider Input: Passage: The bodies of organisms can make a sedimentary rock. Plant bodies are lithified to become coal. When shells are cemented together they make a type of limestone. So limestone can be considered chemical or organic. Answer: coal

Output: What is formed when plant bodies are lithified?

Input: Consider Input: Passage: The ostrich egg - unfertilized, of course. Yes, this egg, just like a human ovum, is just one cell. The egg shell membrane encloses the nucleus containing the genetic material and the cytoplasm. Answer: the nucleus
Output: What part of an egg contains the genetic material ?