The correct answer is (a) Udhamsingh Nagar.
Udhamsingh Nagar is a district in the Indian state of Uttarakhand. It is located in the Kumaon region of the state. The district is named after Udham Singh Nagar, a freedom fighter who was born in the district.
The district is mostly in the Tarai region. The Tarai region is a flat, fertile plain that lies in the foothills of the Himalayas. The region is known for its agriculture and its wildlife.
The other options are incorrect because they are not located in the Tarai region. Dehradun is the capital of Uttarakhand and is located in the Garhwal region of the state. Almora is a district in the Kumaon region of the state. Tehri is a district in the Garhwal region of the state.