The correct answer is: a) Trade between India and Tibet.
The Nathu La Pass is a high mountain pass in the Himalayas on the border between India and China. It is located in the Sikkim state of India and the Tibet Autonomous Region of China. The pass is 4,310 meters (14,140 feet) above sea level and is open for trade and tourism.
The Nathu La Pass was closed in 1962 after the Sino-Indian War. It was reopened in 2006 as part of a thaw in relations between India and China. The reopening of the pass has been significant for trade between India and Tibet. The pass is now used to transport goods between the two countries, and it has also become a popular tourist destination.
The other options are incorrect because:
- Option b) is incorrect because the Nathu La Pass is not a major pilgrimage route.
- Option c) is incorrect because the Nathu La Pass is not a major military route.
- Option d) is incorrect because the Nathu La Pass is not a major cultural exchange route.