Question

a cell gains energy by combining glucose with oxygen in a series of chemical reactions. the products are carbon dioxide and water. what is the source of this energy?
(d) the kinetic energy of oxygen molecules
(e) strong forces within the atomic nuclei of the reactants
(c) the breaking of chemical bonds within the molecules of the products
(b) the breaking of chemical bonds within the molecules of the reactants
(a) the forces that attract protons and neutrons within carbon nuclei

Explanation:

In a chemical reaction like glucose combining with oxygen (cellular respiration), the energy comes from the breaking of chemical bonds within the reactant molecules (glucose and oxygen). When bonds break, energy is released. Options A refers to nuclear forces (not relevant here), C is about product bonds (but energy is from reactant bonds breaking), D is kinetic energy of oxygen (not the source), E is strong forces in atomic nuclei (nuclear, not chemical).

Answer:

B. the breaking of chemical bonds within the molecules of the reactants