The correct answer is b) Idukki.
Idukki is the highest district in Kerala, with an average elevation of 1,200 meters (3,900 feet). The district is home to the Anamudi Peak, the highest peak in Kerala, which has an elevation of 2,695 meters (8,842 feet).
Munnar is a town in the Idukki district, and is known for its tea plantations and scenic views. The town has an elevation of 1,600 meters (5,200 feet).
Wayanad is a district in the northern part of Kerala, and is known for its forests, wildlife, and coffee plantations. The district has an average elevation of 700 meters (2,300 feet).
Pathanamthitta is a district in the central part of Kerala, and is known for its temples, churches, and backwaters. The district has an average elevation of 300 meters (980 feet).