The Prime Minister of which neighbouring country attended the river festival Namami Brahmaputra in India?

Introduction / Context:
This question checks knowledge of regional diplomacy and cultural events involving India and its neighbours. Namami Brahmaputra was a large river festival organized in Assam to celebrate the cultural, ecological, and economic importance of the Brahmaputra river. The presence of foreign leaders at such events reflects diplomatic ties and symbolic gestures of friendship. Identifying which neighbouring country's Prime Minister attended the festival tests awareness of India's relations with South Asian neighbours.

Given Data / Assumptions:

• Namami Brahmaputra was organized as a major river festival in Assam.
• The options are Bhutan, China, Nepal, and Bangladesh, all neighbouring countries of India.
• The question asks specifically which country's Prime Minister attended the festival.
• We assume standard reporting of diplomatic visits in connection with the festival.

Concept / Approach:
Bhutan and India share close and friendly relations, and Bhutanese leaders often participate in significant events in India. For the Namami Brahmaputra festival, the Prime Minister of Bhutan, Tshering Tobgay, was invited as a special guest and attended the inauguration. While Bangladesh and Nepal also share river systems and cultural ties with India, their leaders did not play that specific ceremonial role at this event. China is not represented by its Prime Minister in such state level cultural festivals in India in this manner. Therefore, Bhutan is the correct answer.

Step-by-Step Solution:
Step 1: Recall that Namami Brahmaputra was held in Assam as a celebration of the Brahmaputra river. Step 2: Remember that India invited a foreign head of government to underline regional friendship and shared Himalayan river systems. Step 3: Identify that the visiting leader was the Prime Minister of Bhutan, Tshering Tobgay. Step 4: Eliminate China, Nepal, and Bangladesh as their leaders did not attend the opening of this particular festival in the role mentioned.

Verification / Alternative check:
News reports and official state government releases from the time of the festival mention that the President of India inaugurated the festival and that the Prime Minister of Bhutan attended as a distinguished guest. There is no mention of the Prime Ministers of China, Nepal, or Bangladesh playing an equivalent role in this specific event. This corroborates that Bhutan is the correct answer for which neighbour's Prime Minister attended.

Why Other Options Are Wrong:
China, while an important regional power, does not typically have its Prime Minister attend state level cultural festivals in India like Namami Brahmaputra. Nepal and Bangladesh maintain close relations with India and share river systems, but their Prime Ministers did not attend this particular festival in the capacity indicated in the question. Therefore, selecting any of these countries would not match the documented diplomatic participation.

Common Pitfalls:
A common mistake is to assume that Bangladesh, because of shared river issues and the Brahmaputra basin, must necessarily be the answer. Another error is guessing Nepal due to its Himalayan connection. Candidates may also overthink the strategic implications of China. To avoid these pitfalls, one should rely on specific memories of news coverage rather than general geographic logic alone.

Final Answer:
The Prime Minister of Bhutan attended the Namami Brahmaputra river festival in India.