The correct answer is: D. None of the above
Sirmaur is a district in the Indian state of Himachal Pradesh. It is located in the south-eastern part of the state, and is bordered by the districts of Solan, Shimla, Kullu, Mandi, and Bilaspur. The district has a population of over 700,000 people, and its headquarters is the town of Nahan.
Shimla is the capital of the Indian state of Himachal Pradesh. It is located in the northern part of the state, and is bordered by the districts of Kullu, Mandi, Solan, and Sirmaur. The city has a population of over 200,000 people, and is a popular tourist destination.
The mountain range that separates Sirmaur from Shimla is the Shiwalik Hills. The Shiwaliks are a sub-range of the Himalayas, and are located in the northern Indian states of Punjab, Haryana, Himachal Pradesh, and Uttarakhand. The range is about 2,400 kilometers long, and has an average elevation of about 1,000 meters.
The Shiwaliks are a major tourist destination, and are known for their scenic beauty. The range is also home to a number of wildlife sanctuaries, including the Rajaji National Park and the Corbett National Park.
The other options are incorrect because they are not mountain ranges that separate Sirmaur from Shimla.