The correct answer is: C. Children under age 18 years
Article 15 prohibits discrimination on the grounds of religion, race, caste, sex, or place of birth. Article 16 prohibits discrimination in matters of public employment on the grounds of religion, race, caste, sex, descent, place of birth, residence, or any of them. Article 19 guarantees the right to freedom of speech and expression, the right to assemble peaceably and without arms, the right to form associations or unions, the right to move freely throughout the territory of India, the right to reside and settle in any part of the territory of India, and the right to practice any profession, or to carry on any occupation, trade or business. Article 29 guarantees the right of any section of citizens residing in any part of the territory of India to conserve their culture, language, and script. Article 30 guarantees the right of minorities to establish and administer educational institutions of their choice.
Children under the age of 18 years are not entitled to all of these rights. For example, they do not have the right to vote or to hold public office. They also have some restrictions on their freedom of speech and expression. However, they do have the right to education and to be protected from exploitation.
Option A is incorrect because NRIs are Indian citizens who are living outside of India. They are entitled to all of the fundamental rights, except for the right to vote and to hold public office.
Option B is incorrect because aliens are not Indian citizens. They are not entitled to any of the fundamental rights.
Option D is incorrect because children under the age of 18 years are not entitled to all of the fundamental rights.