Explanation:

This question asks for the definition of 'child' as per the Juvenile Justice (Care and Protection of Children) Act, 2015. The age criterion is a fundamental aspect of this legislation, determining who falls under its protective and rehabilitative framework. Let's analyze each option: Option (1): "Twelve years of age." This option is incorrect. While age 12 might be relevant in some other legal contexts (e.g., for consent in certain matters), it is not the defining age for a 'child' under the Juvenile Justice Act, 2015. The Act aims to protect and rehabilitate a broader age group of individuals who are considered minors. Option (2): "Eighteen years of age." This is the correct option. Section 2(12) of the Juvenile Justice (Care and Protection of Children) Act, 2015, explicitly defines a 'child' as "a person who has not completed eighteen years of age." This definition is crucial as it sets the upper age limit for individuals to be considered juveniles under the Act, ensuring that anyone below this age receives the special care, protection, and rehabilitation provisions outlined in the law, rather than being subjected to the adult criminal justice system. This age aligns with international standards for the definition of a child, such as those set by the UN Convention on the Rights of the Child. Option (3): "Fifteen years of age." This option is incorrect. Prior to the 2015 Act, some older laws or specific provisions might have used different age cut-offs, but under the current Juvenile Justice Act, 2015, fifteen years is not the age that defines a 'child'. The Act specifically raised the age to eighteen to provide more comprehensive protection. Option (4): "Sixteen years of age." This option is incorrect. While the 2015 Act introduced provisions for children in conflict with the law between the ages of 16 and 18 to be tried as adults for heinous offences in certain circumstances (Section 15), the *definition* of a 'child' itself remains as a person who has not completed eighteen years of age. The provision for trial as an adult is an exception to the general rule, not a redefinition of 'child' for the purposes of the Act. Therefore, sixteen years is not the age that defines a 'child' under the Act.