The correct answer is: a) North Eastern Coastal Plain
The North Eastern Coastal Plain is the region of Odisha that receives the highest average annual rainfall. This is due to the fact that this region is located in the path of the southwest monsoon winds, which bring heavy rains to the region. The average annual rainfall in the North Eastern Coastal Plain is about 1,500 mm.
The East and South Eastern Coastal Plain also receives a significant amount of rainfall, with an average annual rainfall of about 1,200 mm. However, the North Eastern Coastal Plain receives more rainfall because it is located closer to the Bay of Bengal, which is the source of the southwest monsoon winds.
The North Central Plateau and the Western Undulating Plateau receive less rainfall than the coastal plains. The average annual rainfall in the North Central Plateau is about 1,000 mm, and the average annual rainfall in the Western Undulating Plateau is about 800 mm. This is because these regions are located further away from the Bay of Bengal and are not in the path of the southwest monsoon winds.