The correct answer is: A. Lahaul and Spiti.
Yunam-So Lake is a high-altitude lake located in the Lahaul and Spiti district of Himachal Pradesh, India. It is situated at an elevation of 4,400 meters (14,400 feet) above sea level, and is one of the highest lakes in the world. The lake is a popular tourist destination, and is known for its stunning scenery and clear waters.
The lake is fed by a number of glaciers, and is surrounded by snow-capped mountains. The lake is home to a variety of wildlife, including snow leopards, ibex, and marmots. The lake is also a popular destination for birdwatching.
The lake is accessible by foot or by horseback. The best time to visit the lake is during the summer months, when the weather is warm and the lake is full of water.
The other options are incorrect because:
- Option B, Mandi, is a district in Himachal Pradesh, but Yunam-So Lake is not located in this district.
- Option C, Kinnaur, is a district in Himachal Pradesh, but Yunam-So Lake is not located in this district.
- Option D, Kullu, is a district in Himachal Pradesh, but Yunam-So Lake is not located in this district.