The correct answer is C. Idukki.
Agastyamalai Biosphere Reserve is a protected area in the Western Ghats of India. It is located in the state of Kerala, and covers an area of 3,860 square kilometers. The reserve is home to a variety of plant and animal life, including several endangered species. It is also a popular tourist destination, known for its scenic beauty and its many temples and shrines.
Pathanamthitta is a district in the state of Kerala, India. It is located in the central part of the state, and is bordered by the districts of Alappuzha, Kottayam, Idukki, and Thrissur. The district has a population of over 2.5 million people, and its headquarters is the town of Pathanamthitta.
Thiruvananthapuram is the capital of the state of Kerala, India. It is located on the Malabar Coast, and is the southernmost state capital in India. The city has a population of over 1 million people, and is known for its beautiful beaches, its temples, and its palaces.
Idukki is a district in the state of Kerala, India. It is located in the central part of the state, and is bordered by the districts of Pathanamthitta, Kottayam, Ernakulam, and Thrissur. The district has a population of over 3 million people, and its headquarters is the town of Idukki.
Wayanad is a district in the state of Kerala, India. It is located in the northern part of the state, and is bordered by the states of Karnataka and Tamil Nadu. The district has a population of over 800,000 people, and its headquarters is the town of Kalpetta.