The correct answer is option (C), Una.
The Shiwalik hills are a sub-range of the Himalayas that run parallel to the main Himalayan range in the Indian states of Himachal Pradesh, Uttarakhand, Haryana, Punjab, and Delhi. The Shiwalik hills are a popular tourist destination, known for their scenic beauty and wildlife.
The district of Una is located in the state of Himachal Pradesh, and is fully located in the Shiwalik hills. The district is known for its natural beauty, with a number of rivers and streams flowing through it. Una is also home to a number of historical and religious sites, including the Una Devi Temple and the Chamunda Devi Temple.
The other options are incorrect because they are not fully located in the Shiwalik hills. Kangra district is located in the Kangra Valley, which is a part of the Dhauladhar Range. Solan district is located in the Solan Valley, which is a part of the Pir Panjal Range. Sirmaur district is located in the Sirmaur Hills, which are a part of the Mahabharat Range.