The correct answer is: a) High-altitude passes.
Wind power is a renewable energy source that can be used to generate electricity. It is a clean and efficient way to produce power, and it does not produce any emissions. Wind turbines are used to convert the kinetic energy of the wind into electricity.
Sikkim is a state in India that is located in the Himalayas. The state has a high altitude and a mountainous terrain. This makes it an ideal location for wind power development. The high altitude passes in Sikkim are exposed to strong winds, which makes them ideal for the construction of wind turbines.
The other options are not as suitable for wind power development. Coastal regions are often windy, but they are also prone to storms and hurricanes. This can damage wind turbines and make them difficult to maintain. River valleys are also windy, but they are often narrow and have a lot of vegetation. This can make it difficult to build wind turbines in river valleys. Dense forests are not suitable for wind power development because they block the wind.
In conclusion, the correct answer is: a) High-altitude passes.