The correct option is "3 only" because souring of milk represents a chemical change where the composition of the milk is altered due to the action of bacteria, resulting in the formation of new substances (such as lactic acid). In contrast, the crystallization of sodium chloride is a physical change where the salt's physical form is altered but its chemical composition remains the same; similarly, melting of ice is a phase change that does not involve a change in the chemical structure of water. Understanding these distinctions is fundamental in chemistry and aligns with concepts covered in standard educational materials such as NCERT.