Which one of the following countries shares the longest international boundary with India?

Introduction / Context:
India shares land frontiers with several neighbouring countries, and the length of these boundaries is a favourite topic in competitive exams. This question asks you to identify which country has the longest international boundary with India. Understanding these boundary lengths helps you appreciate the geopolitical and geographic importance of India's neighbours.

Given Data / Assumptions:

• The neighbouring countries listed are Bangladesh, Bhutan, China and Pakistan.
• The question focuses on the length of the shared boundary, not on area, trade or population.
• We assume the standard figures in which the India Bangladesh border is the longest among India's land boundaries.
• Minor variations in reported kilometre values in different sources do not change the ranking order.

Concept / Approach:
India has long boundaries with both China and Bangladesh, but the boundary with Bangladesh is highly indented and wraps around large portions of north eastern India, producing a greater total length. The best approach is to recall the approximate order of boundary lengths Bangladesh first, China second, Pakistan third and Bhutan much shorter. This ranking allows you to identify the correct option quickly.

Step-by-Step Solution:
Step 1: Visualise the map of eastern India where Bangladesh lies almost surrounded on three sides by Indian territory, especially West Bengal, Assam, Meghalaya, Tripura and Mizoram.Step 2: Compare this with the northern boundary with China, which is long but follows a relatively continuous high mountain frontier along the Himalaya and associated ranges.Step 3: Recall that the Pakistan boundary, though important historically and politically, is shorter than the boundary with Bangladesh.Step 4: Recognise that Bhutan is a small landlocked country and has the shortest boundary length among the options, so Bangladesh must be the correct answer.

Verification / Alternative check:
Official data and standard geography references consistently show that the India Bangladesh border is the longest among India's land boundaries, measured in thousands of kilometres. The intricate nature of this boundary, with several enclaves and river courses, contributes to this large value. Cross checking with a quantitative table in an atlas or textbook will confirm this fact.

Why Other Options Are Wrong:
Bhutan is clearly incorrect because it is a small Himalayan kingdom with a relatively short border shared only with a limited stretch of Indian states. China does share a long mountain boundary with India, but its total length is still less than that of the India Bangladesh boundary. Pakistan also has a significant frontier with India across the Thar Desert and Punjab plains, but again its total length is smaller than that of the border with Bangladesh.

Common Pitfalls:
Many students choose China or Pakistan because they remember recent news or conflicts more readily than boundary length data. Another pitfall is to confuse longest boundary with total area of the neighbouring country, even though a large country like China does not necessarily share the longest stretch with India. Systematically revising boundary statistics helps to avoid these intuitive but incorrect choices.

Final Answer:
The country that has the longest international boundary with India is Bangladesh.