The correct answer is option (D), Kinnaur.
Shillai is the highest peak in Kinnaur district of Himachal Pradesh. It is located in the Zanskar Range of the Himalayas. The peak is 6,543 meters (21,467 ft) above sea level. It is a popular trekking destination.
Option (A), Chamba, is a district in Himachal Pradesh. It is located in the western part of the state. The district is home to several high peaks, including the Dhauladhar Range. However, Shillai is not located in Chamba district.
Option (B), Bilaspur, is a district in Himachal Pradesh. It is located in the central part of the state. The district is home to several high peaks, including the Shimla Hills. However, Shillai is not located in Bilaspur district.
Option (C), Hamirpur, is a district in Himachal Pradesh. It is located in the central part of the state. The district is home to several high peaks, including the Dhauladhar Range. However, Shillai is not located in Hamirpur district.