Answer:
Explanation:
Chemical reactions that release energy are called exothermic. In exothermic reactions, more energy is released when the bonds are formed in the products than is used to break the bonds in the reactants. Exothermic reactions are accompanied by an increase in temperature of the reaction mixture.
The Doppler effect is the term that best describes the change in frequency of waves when there is motion between the source of the waves and the observer. The correct option among all the options that are given in the question is the first option or option "a". I hope the answer helps you.