Which of the following gases is noted as a promising alternative to fossil fuels?

Hydrogen is considered a promising alternative to fossil fuels due to its potential for clean energy production. When burned or used in fuel cells, hydrogen produces only water as a byproduct, contributing to a reduction in greenhouse gas emissions and air pollutants compared to fossil fuels that release carbon dioxide and other harmful substances.

Additionally, hydrogen can be produced from various renewable energy sources, such as water through electrolysis using solar or wind power, making it a versatile and sustainable fuel. This characteristic positions hydrogen as a key player in the transition towards more sustainable energy systems, aiming to reduce our reliance on fossil fuels and mitigate climate change.

In contrast, carbon dioxide is a greenhouse gas typically produced by burning fossil fuels, and while methane does have applications as a cleaner fossil fuel, it is still a hydrocarbon that can contribute to greenhouse gas emissions if not managed properly. Nitrogen dioxide is primarily a pollutant from combustion processes and does not serve as a viable alternative to fossil fuels.