Answer: Option (a) is the correct answer.
Explanation:
A process in which heat is absorbed by the atoms of a substance is known as endothermic process. Here, energy of products is more than the energy of reactants.
Whereas a process in which heat is released by the atoms of a substance is known as exothermic process. Here, energy of reactants is more than the energy of products.
So, when milk boils then energy is releasing in the form of steam. When wax melts then it means heat is absorbed by wax molecules.
When water freezes then also energy is absorbed due to which molecules are coming closer to each other.
Whereas evaporation and heating of water will are also endothermic as heat is absorbed in both the cases.
Thus, we can conclude that boiling of milk is an example of an exothermic process.