One challenge Sikkim faced after its merger with India was:

The correct answer is: d) All of the above

Sikkim was a monarchy until 1975, when it merged with India. This merger led to a number of challenges, including:

• Integrating different administrative systems: Sikkim had its own unique system of government, which was based on the Buddhist religion. This system had to be merged with the Indian system of government, which is based on the Constitution of India.
• Addressing economic disparities: Sikkim was a relatively poor state, and there were significant economic disparities between different groups of people. These disparities had to be addressed in order to ensure that all people in Sikkim benefited from the merger with India.
• Reconciling with former supporters of the Chogyal: The Chogyal was the hereditary ruler of Sikkim until 1975. Many people in Sikkim were loyal to the Chogyal, and they were not happy about the merger with India. These people had to be reconciled with the merger in order to ensure stability in Sikkim.

These challenges were significant, but they were eventually overcome. Sikkim is now a thriving state in India, and it has made significant progress in terms of economic development and social justice.