Explanation:

The Rangit Dam is a run-of-the-river power project on the Ranjit River, a major tributary of the Tista River, in the South Sikkim district of Sikkim. The dam is 45 metres high concrete gravity structure of 100 metres length. The reservoir created behind the dam has a storage capacity of 1,175,000 cubic metres. The average annual power generation from the 60 MW (3×20 MW) project is 340 GWh with firm power of 39 MW. Hence, answer is a.