Q.Which of the following is a fuel gas ?

Renewable and Alternative Energy Sources

Every time we burn coal, petrol or diesel, we do two harmful things at once: we use up a resource that took millions of years to form, and we release carbon dioxide and other pollutants into the air. Renewable energy sources exist to break out of this trap — they draw on flows of energy that nature keeps refilling, so using them today does not empty the tank for tomorrow.

Why "renewable" matters

The core idea is rate of replacement. Sunlight arrives every day, wind keeps blowing, rivers keep flowing, and plants keep growing. Because these are continuously renewed, they can supply energy indefinitely without being exhausted — unlike fossil fuels, which are finite. This is what makes renewables central to sustainable development: meeting present needs without robbing future generations.

The main clean options

• Solar energy — sunlight is captured either as heat (solar cookers, water heaters) or converted directly to electricity by photovoltaic (solar) cells. It is abundant across most of India and produces no pollution while running.
• Wind energy — moving air turns turbine blades that drive a generator.
• Hydro energy — falling or flowing water spins turbines in dams.
• Biogas and biomass — plant and animal waste is broken down by microbes to yield methane-rich fuel gas.
• Hydrogen fuel — hydrogen burns (or reacts in a fuel cell) to give energy, and its only product is water, making it an exceptionally clean fuel.

The advantages, in one line each …