Reasons for the Partition of British India:
The partition of British India was primarily driven by communal tensions between Hindus and Muslims, as well as political and administrative considerations. Several factors contributed to the eventual division of the country:

1. Communal Tensions: The Hindu-Muslim divide had been growing since the late 19th century, with the formation of various religious and political organizations advocating for the rights and interests of their respective communities. The demand for separate electorates based on religion further deepened these divisions.

2. Two-Nation Theory: The concept of the Two-Nation Theory, propagated by Muslim leaders like Muhammad Ali Jinnah, argued that Hindus and Muslims were distinct nations with separate identities, cultures, and interests. This theory laid the foundation for the demand for a separate Muslim-majority nation.

3. Political Struggles: The Indian National Congress, initially a party representing diverse interests, became dominated by Hindus, which led to disillusionment among many Muslim leaders. The Muslim League, led by Jinnah, demanded the creation of a separate Muslim state known as Pakistan.

4. British Divide and Rule: The British, in their effort to maintain control over India, exploited communal tensions and differences between Hindus and Muslims. They adopted policies that favored one community over the other, exacerbating the divide.

Failure of the Last Attempt to Keep India United:
The last attempt to keep India united was the Cabinet Mission Plan of 1946, which proposed a decentralized federal system. However, it failed due to the following reasons:

1. Communal Differences: The Hindu and Muslim leaders had divergent visions for the future of India. The Muslim League insisted on the creation of Pakistan, while the Congress favored a united India. Despite efforts to find a middle ground, the communal differences were too deep to reconcile.

2. Power Struggles: Both the Congress and the Muslim League were unwilling to compromise on their positions. The power struggle for control over the central government and the fear of domination by one community over the other made reaching a consensus difficult.

3. Mountbatten's Deadline: Lord Mountbatten, the last British Viceroy of India, set a deadline for the transfer of power by June 1948. This accelerated the negotiations and limited the time available to resolve complex issues, making it difficult to reach a satisfactory agreement.

4. Violence and Communal Riots: The outbreak of communal violence and riots in various parts of the country intensified the divide between Hindus and Muslims. The deteriorating law and order situation made it increasingly challenging to maintain a united India.

Ultimately, the failure to address the deep-rooted communal tensions, the inability to find a mutually acceptable solution, and the imposition of a strict deadline led to the partition of British India and the creation of India and Pakistan in 1947.