Explanations:The referendum to decide whether Sikkim should merge with the Indian Union was a significant political event that took place on 14th April, 1975. This referendum was a crucial step in the political history of Sikkim, as it marked the transition from a protectorate to a full-fledged state of India.
Sikkim, located in the Himalayan region, had a unique political status before the referendum. It was a protectorate of India, which meant that while it had its own monarchy and government, India was responsible for its defense, foreign affairs, and communications. The decision to hold a referendum was a result of political negotiations and the desire to integrate Sikkim more closely with the Indian Union.
The referendum was held to gauge the public opinion of the Sikkimese people on the issue of merging with India. The result of the referendum was overwhelmingly in favor of the merger, with a vast majority of the voters supporting the proposal. Following the referendum, Sikkim officially became the 22nd state of India on 16th May, 1975.
Understanding the historical context of this referendum is important for students preparing for competitive examinations, as it is a significant event in the political history of India. The date 14th April, 1975, is a key date to remember, as it marks the culmination of a process that led to the integration of Sikkim into the Indian Union.
It is important to note that the other dates mentioned in the options (14th April, 1980; 9th May, 2000; and 10th May, 1999) are not related to the referendum for Sikkim's merger with India. These dates might be associated with other events in Sikkim's history, but they are not relevant to the specific question of the referendum.
Therefore, the correct answer is 14th April, 1975, as it is the date when the referendum was held to decide whether Sikkim should merge with the Indian Union.