In a chemical reaction, the reactants are substances that undergo the reaction, and the products are substances that are formed during the reaction. the table below shows the reactants and products of several different chemical reactions. reactants products type of reaction 4k + o2] [2k2o + heat] exothermic 2h2o + heat] [2h2 + o2] endothermic 2co + o2] [2co2 + heat] exothermic caco3 + hea] [cao + co2] endothermic based on the information given in the above table, the best definition of an endothermic reaction would be? a. a reaction that releases heat. b. a reaction that absorbs heat. c. a reaction that has one product. d. a reaction that does not require heat.