Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Acetylene is an interesting example of a molecule with two central atoms, which are both C atoms. Polyatomic ions are bonded together with covalent bonds. Because they are ions, however, they participate in ionic bonding with other ions. So both major types of bonding can occur at the same time. Answer: acetylene
A:
What is an interesting example of a molecule with two central atoms, which are both c atoms?