1. C2H2 (Acetylene): Acetylene is a colorless gas with a faint garlic-like odor. It is highly flammable and is commonly used in welding and cutting metals.

2. C2H4 (Ethylene): Ethylene is a colorless gas with a slightly sweet odor. It is a plant hormone that regulates growth and development, and is also used in the production of plastics and synthetic rubber.

3. CO2 (Carbon Dioxide): Carbon Dioxide is a colorless and odorless gas that is produced by the combustion of fossil fuels and the respiration of living organisms. It is a greenhouse gas that contributes to global warming.

4. SO2 (Sulfur Dioxide): Sulfur Dioxide is a colorless gas with a pungent odor. It is produced by the burning of fossil fuels and is a major air pollutant that can cause respiratory problems and acid rain.