The correct answer is option 'C' which is Equality. The principle of Equality has been emphasized by the Supreme Court as an essential feature of the Constitution.

Explanation:

The Preamble of the Constitution of India lays down the fundamental values and principles on which the Constitution is based. It acts as the guiding light for the interpretation and implementation of the Constitution. The Preamble declares India to be a sovereign, socialist, secular, and democratic republic. It also enshrines the principles of justice, liberty, equality, and fraternity.

The principle of equality is a fundamental aspect of the Indian Constitution. It ensures that all individuals are treated equally before the law and have equal opportunities. The Supreme Court has played a crucial role in upholding and interpreting the principle of equality in various cases.

1. Equal protection of laws: The Supreme Court has emphasized the principle of equality by interpreting Article 14 of the Constitution which guarantees the right to equality. It has held that the State must not discriminate between individuals or groups and should provide equal protection of laws to everyone.

2. Prohibition of discrimination: The Supreme Court has struck down laws that discriminate on the basis of caste, religion, gender, or any other grounds. It has held that such discrimination violates the principle of equality.

3. Affirmative action: The Supreme Court has recognized the need for affirmative action to ensure equality for historically disadvantaged groups. It has upheld reservations in educational institutions and government jobs for Scheduled Castes, Scheduled Tribes, and Other Backward Classes.

4. Gender equality: The Supreme Court has played a vital role in promoting gender equality. It has struck down discriminatory laws and practices, and has recognized the rights of women to equality, dignity, and freedom from discrimination.

5. Economic equality: The Supreme Court has also emphasized the principle of economic equality. It has held that the State has a duty to reduce economic inequalities and ensure social and economic justice.

In conclusion, the Supreme Court has consistently emphasized the principle of equality as an essential feature of the Constitution. It has interpreted and applied the principle of equality in various cases to ensure that all individuals are treated equally before the law and have equal opportunities.