Gas that helps in burning: Oxygen

Explanation:

When a substance burns, it reacts with oxygen in the air to produce heat and light. Oxygen is a highly reactive gas and supports combustion.

Combustion:

Combustion is a chemical reaction that occurs when a fuel combines with oxygen in the presence of heat to produce heat, light, and other products. It is also known as burning.

Oxygen's role in combustion:

Oxygen is essential for combustion to occur. It acts as an oxidizing agent, which means it helps in the oxidation of the fuel. During combustion, oxygen molecules break apart and combine with the fuel molecules, releasing energy in the process.

Combustion equation:

The general equation for combustion is:
Fuel + Oxygen → Carbon Dioxide + Water + Energy

For example, in the combustion of methane (CH4):
CH4 + 2O2 → CO2 + 2H2O + Energy

Other gases and combustion:

- Nitrogen (N2): Nitrogen is an inert gas and does not support combustion. It does not react easily with other substances and remains unchanged during the combustion process.

- Carbon Dioxide (CO2): Carbon Dioxide is a product of combustion. It is formed when carbon-containing fuels burn completely in the presence of oxygen.

- Carbon Monoxide (CO): Carbon Monoxide is a toxic gas that is produced when carbon-containing fuels do not burn completely due to insufficient oxygen. It is a product of incomplete combustion and can be dangerous in enclosed spaces.

Conclusion:

Among the given options, oxygen is the gas that helps in burning. It supports combustion by combining with the fuel and releasing energy. Nitrogen is inert and does not participate in combustion. Carbon Dioxide is a product of complete combustion, and Carbon Monoxide is a product of incomplete combustion.