Correct Option: C [ West Bengal ]
Remark:
Explanation: The Indian state that shares the longest border with Bangladesh is West Bengal. The total length of the India–Bangladesh border is approximately 4,096 km, making it the fifth-longest international border in the world. Out of this, about 2,217 km is shared by West Bengal alone. Other Indian states that share borders with Bangladesh are Assam, Meghalaya, Tripura, and Mizoram. This border is crucial for trade, cultural exchange, and regional connectivity between the two nations.