Explanation:

The Preamble of the Indian Constitution is a brief introductory statement that sets out the objectives and purposes of the Constitution. It reads as follows:

"We, the people of India, having solemnly resolved to constitute India into a Sovereign Socialist Secular Democratic Republic and to secure to all its citizens:

Justice, social, economic and political;

Liberty of thought, expression, belief, faith and worship;

Equality of status and of opportunity;

and to promote among them all

Fraternity assuring the dignity of the individual and the unity and integrity of the Nation;

In our Constituent Assembly this twenty-sixth day of November 1949, do hereby adopt, enact and give to ourselves this Constitution."

The Preamble of the Indian Constitution declares India to be a Sovereign, Socialist, Secular, Democratic Republic. The correct option is 'D', which includes all these four terms.

Let us understand each term in detail:

1. Sovereign: India is a sovereign nation, which means it is free from external control and has the power to govern itself. India is not subject to any external authority and is free to conduct its internal and external affairs without any interference.

2. Socialist: India is a socialist country, which means the government plays a significant role in regulating the economy and providing social welfare services to its citizens. The Constitution aims to promote social, economic, and political justice, and the government is responsible for ensuring the welfare of its citizens.

3. Secular: India is a secular country, which means the government does not promote any particular religion and treats all religions equally. The Constitution guarantees freedom of religion to all its citizens and prohibits discrimination on the basis of religion.

4. Democratic: India is a democratic country, which means the power to govern is vested in the hands of the people. The Constitution provides for a representative form of government, where citizens elect their representatives to make laws and govern the country.

Conclusion:

In summary, the Preamble of the Indian Constitution declares India to be a Sovereign, Socialist, Secular, Democratic Republic. These four terms are essential to understand the nature and objectives of the Indian Constitution.