To rank India's electricity generation sources by total power generation capacity, from highest to lowest, we must consider each source's contribution. India's main sources are:
- Thermal: Comprising coal, gas, and oil, this sector dominates due to existing infrastructure and resource availability. Consequently, thermal power generally possesses the highest capacity in India.
- Hydro: This renewable source holds significant capacity, leveraging the nation's numerous large rivers.
- New and Renewable Energy: This category encompasses wind, solar, and other renewable technologies. Although experiencing rapid expansion, it typically ranks below thermal and hydro in total capacity.
- Nuclear: This source constitutes a smaller segment of India's power generation, attributed to a limited number of facilities and substantial initial investment.
Following this assessment, the sequence of power generation sources from highest to lowest capacity is: Thermal, Hydro, New and Renewable Energy, and Nuclear.
Therefore, the correct answer is: (B), (D), (C), (A)