The correct answer is option 'A', Nathu La Pass.

Nathu La Pass is a famous mountain pass that connects India and China in the state of Sikkim. It is located in the eastern Himalayas at an altitude of 4,310 meters (14,140 feet) above sea level. The pass is a part of the ancient Silk Route and has historical significance as a trade route between India and Tibet.

Nathu La Pass has played a crucial role in the cultural, economic, and political exchanges between the two countries for centuries. It was closed in 1962 during the Sino-Indian war but was reopened in 2006 as a border trade route after extensive renovations and negotiations between India and China.

Key Points:

1. Location: Nathu La Pass is situated in the Gangtok district of Sikkim, a northeastern state of India. It lies on the border of India's Sikkim and China's Tibet Autonomous Region.

2. Historical Significance: The pass has been an important trade route for centuries, connecting the Indian subcontinent with Central Asia. It was a major route for the silk trade during ancient times.

3. Sino-Indian War: During the Sino-Indian war of 1962, Nathu La Pass witnessed intense fighting between the Indian and Chinese armies. The pass was closed after the war, leading to a halt in trade and cultural exchanges.

4. Reopening and Border Trade: After several rounds of negotiations, Nathu La Pass was reopened in 2006 for border trade between India and China. It is one of the four officially designated border trade points between the two countries.

5. Importance for Tourism: Nathu La Pass has become a popular tourist destination due to its strategic location, stunning views of the Himalayas, and historical significance. Visitors can obtain a permit to visit the pass and experience the unique blend of Indian and Tibetan cultures.

In conclusion, Nathu La Pass is the famous pass that connects India and China in Sikkim. With its historical significance, strategic location, and cultural exchanges, it serves as a crucial link between the two nations.