The correct answer is (a) 7138 m.
Nandakot is a mountain peak in the Himalayas, located in the Bagmati Zone of central Nepal. It is the 12th highest peak in Nepal and the 74th highest peak in the world. The mountain is located about 50 kilometers (31 mi) east of Kathmandu, the capital of Nepal.
Nandakot is a popular trekking destination, and there are several trails that lead to the summit. The most popular trail starts from the village of Chisapani, which is located about 30 kilometers (19 mi) from Kathmandu. The hike from Chisapani to the summit of Nandakot takes about two days.
The best time to trek to Nandakot is during the spring (March-May) or autumn (September-November). The weather during these seasons is generally clear and sunny, with cool temperatures at night.
The views from the summit of Nandakot are spectacular. On a clear day, it is possible to see the Annapurna range, the Langtang range, and the Everest range.
Here is a brief description of each option:
(a) 7138 m: This is the correct answer. Nandakot is 7138 meters high.
(b) 6400 m: This is the height of Mount Everest, the highest mountain in the world.
(c) 6861 m: This is the height of Dhaulagiri, the seventh highest mountain in the world.
(d) 6320 m: This is the height of Manaslu, the eighth highest mountain in the world.