Among the options provided, a poorly developed infrastructure has been a significant factor contributing to India's economic struggles.
While inadequate investment in productive capital and isolation from other countries can also pose challenges, the lack of well-developed infrastructure—such as transportation, energy, and communication networks—has a direct impact on economic efficiency, productivity, and growth. Poor infrastructure can hinder trade, increase logistics costs, and limit access to markets and services, ultimately affecting the overall economic development of the country.
So, while other factors may contribute, poorly developed infrastructure is often cited as a major constraint on India's economic performance.