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

Example Input: Passage: Carbon doesn't stop there. Living things get energy from food in a process called respiration. This releases carbon dioxide back into the atmosphere. The cycle then repeats. Answer: carbon dioxide
Example Output: Living things get energy from food in a process called respiration, which releases what gas back into the atmosphere?

Example Input: Passage: The two materials do have at least one thing in common. The atoms in the materials are held together by covalent bonds. These bonds consist of electrons shared between two or more atoms. Unlike ionic bonds, where electrons are either lost or gained by an atom to form charged ions, electrons in covalent compounds are shared between the two atoms, giving rise to properties that are quite different from those seen in ionic materials. Answer: ionic bonds
Example Output: Electrons in covalent compounds are shared between the two atoms, unlike the case in what type of bonds?

Example Input: Passage: Protons and neutrons are made up of fundamental particles of matter called quarks. Electrons are another type of fundamental particles of matter called leptons. Bosons are fundamental particles that carry forces between fundamental particles of matter. Answer: quarks
Example Output:
A fundamental particle of matter, protons and neutrons are made of these?