Answer : 4. "Arunachal Pradesh"
Explanation :

Prime Minister Narendra Modi recently inaugurated the Sela Tunnel as part of his one-day visit to Arunachal Pradesh. Which is the world's longest twin-lane tunnel. This tunnel connects Tezpur to Tawang near the Line of Actual Control (LAC) with China. Sela Tunnel has been constructed at an altitude of 13,000 feet. It has been constructed by the Border Roads Organization (BRO).