In 1817 , James Mill published his most important work , The History of British India

The book "A History of British India" was written by James Mill.

Explanation:

James Mill was a Scottish philosopher, economist and historian who lived from 1773 to 1836. He is best known for his influential book "The History of British India", which was published in 1817. In this book, Mill provided a comprehensive account of the history of India under British rule, starting from the arrival of the East India Company in the early 1600s to the British conquest of the subcontinent in the late 1700s and early 1800s.

Mill's book was a product of his deep commitment to the Enlightenment ideals of rationalism, progress and individualism. He believed that the British had a mission to civilize and modernize India, and that this could be achieved through a combination of political and economic reforms. He argued that British rule had brought peace, stability and prosperity to India, and that the Indians had much to learn from British culture and institutions.

Despite its many flaws and biases, Mill's book remains an important source for the study of British India. It influenced generations of British and Indian historians, and helped shape the way in which the British understood their imperial mission in India.

NCERT Solutions -The Indian Constitution:

The Indian Constitution is a written document that outlines the framework and principles of the government of India. It was adopted by the Constituent Assembly on November 26, 1949 and came into effect on January 26, 1950. The Constitution is the supreme law of the land, and all other laws and regulations must conform to its provisions.

The Constitution is divided into several parts, each of which deals with a different aspect of the government and society. Some of the key features of the Indian Constitution include:

- Preamble: The Preamble to the Constitution outlines the basic values and principles upon which the Indian state is based. It declares India to be a sovereign, socialist, secular, democratic and republic nation.

- Fundamental Rights: The Constitution guarantees a number of fundamental rights to all citizens of India, including the right to equality, freedom of speech and expression, freedom of religion, and the right to life and liberty.

- Directive Principles of State Policy: These are guidelines and principles that the government is expected to follow in order to promote the welfare of the people. They include provisions for free and compulsory education, protection of the environment, and the promotion of social justice and equality.

- Federal Structure: The Indian Constitution provides for a federal system of government, with powers divided between the central government and the states. The Constitution also includes provisions for the creation of new states and the reorganization of existing ones.

- Independent Judiciary: The Constitution establishes an independent judiciary, with the Supreme Court as the highest court of appeal. The judiciary is responsible for interpreting the Constitution and ensuring that the government acts within the limits of the law.

Overall, the Indian Constitution is a landmark document that reflects the aspirations and ideals of the Indian people. It has played a crucial role in shaping India's political, social and economic development over the past seven decades.