The correct answer is A. Sirmaur.
Sirmaur is a district in the Indian state of Himachal Pradesh. It is located in the central part of the state, and is bordered by the districts of Solan, Shimla, Kullu, Mandi, and Chamba. The district has a population of over 700,000 people, and its headquarters is the town of Nahan.
Sirmaur is a mountainous district, and its terrain is characterized by hills, valleys, and forests. The district is home to a number of rivers, including the Yamuna, the Giri, and the Tons. The climate of Sirmaur is temperate, with hot summers and cold winters.
The district is known for its natural beauty, and is a popular tourist destination. Sirmaur is also home to a number of historical and cultural sites, including the Nahan Fort, the Chamunda Devi Temple, and the Masrur temples.
Borax is a mineral that is used in a variety of industrial and commercial applications. It is found in the form of white, colorless, or yellowish-white crystals. Borax is a naturally occurring mineral, and it is also produced synthetically.
Musk is a substance that is obtained from the musk deer. It is a waxy, reddish-brown substance that is used in perfumes and other cosmetics. Musk is also used in traditional Chinese medicine.
In the modern history of Himachal, Sirmaur was the richest source of borax and musk. The mineral was mined in the district, and the musk was obtained from the musk deer that were found in the forests of Sirmaur. The trade in borax and musk was a major source of income for the people of Sirmaur.
The other options are incorrect because they are not regions in Himachal Pradesh. Tibet is a region in China, and Lahore is a city in Pakistan.