The Nathu La Pass, located on the border between Sikkim and Tibet (Chin

The correct answer is: b) 1988.

The Nathu La Pass is a high mountain pass in the Himalayas on the border between Sikkim, India, and Tibet, China. It is located at an elevation of 4,310 meters (14,140 feet). The pass was closed in 1962 after the Sino-Indian War, but it was reopened for trade in 1988. The pass is a major trade route between India and China, and it is also a popular tourist destination.

Option a) is incorrect because the Nathu La Pass was closed in 1962 after the Sino-Indian War.

Option c) is incorrect because the Nathu La Pass was reopened for trade in 1988, not 2006.

Option d) is incorrect because the Nathu La Pass was reopened for trade in 1988, not 2018.