The correct option is: To restructure its economy through structural adjustment programme

In the immediate post-Independence period of India (starting from 1947), the nation faced three major challenges to its nationhood and development, which are well-documented in its history:
1. Shaping a United Nation: The first and most immediate challenge was to forge a united nation that was accommodative of the immense cultural, linguistic, and religious diversity. The partition of the country had already created deep trauma and division, making national integration a paramount task.
2. Establishing Democracy: The second challenge was to develop democratic practices in accordance with the newly framed Constitution. This involved establishing representative institutions, drafting electoral rules, and conducting free and fair elections for a massive, largely illiterate population.
3. Economic Development and Poverty Eradication: The third challenge was to evolve policies that would ensure economic development and eradicate widespread poverty, focusing on the welfare of the entire society rather than a few select groups.

In contrast, the Structural Adjustment Programme (SAP) refers to a set of economic reforms, typically consisting of loans accompanied by policy conditions from international financial institutions like the International Monetary Fund (IMF) and the World Bank. India did not face this as an immediate challenge in 1947. Instead, India adopted a state-led, mixed economy model with a strong public sector and economic planning. The structural adjustment reforms (economic liberalization) were introduced much later, in 1991, in response to a severe balance of payments crisis. Therefore, restructuring the economy through a structural adjustment programme was not an immediate post-Independence challenge to India's nationhood.