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

Example Input: Passage: The heart is a muscular organ in the chest that consists mainly of cardiac muscle. It pumps blood through blood vessels by repeated, rhythmic contractions. Blood flows through four chambers of the heart when it beats. Heartbeat is controlled by electrical signals from special cells within the heart called the pacemaker. Answer: cardiac muscle
Example Output: What type of muscle makes up most of the heart?

Example Input: Passage: Bonds break and reform during chemical reactions. Reactants and products contain the same atoms, but they are rearranged during the reaction, so reactants and products are different substances. Answer: reactants
Example Output: In a chemical reaction, what, in general, comes together in order to form a product?

Example Input: Passage: Energy is conserved in a closed system. That is, if you add up all the energy of an object(s) at one time it will equal all the energy of said object(s) at a later time. A closed system is a system where no energy is transferred in or out. The total energy of the universe is a constant (i. e. it does not change). The problems below do not consider the situation of energy transfer (called work). So friction and other sources where energy leaves the system are not present. Thus, one simply adds up all the potential energy and kinetic energy before and sets it equal to the addition of the total potential energy and kinetic energy after . Answer: is conserved
Example Output:
What happens to energy in a closed system?