ANSWER: Guwahati
Explanation:
- Lumding comes under North Frontier Railway zone
- Movement of foodgrains to Mizoram, Tripura, south Assam and Manipur takes place through the Barak valley.
- Silchar is the main city of the valley. The railway line is broad gauge from Assam's main city of Guwahati up to Lumding (in southern Assam).
- The rail line brings Assam's underdeveloped but strategically important Barak Valley on the broad gauge map.