What is the gas stream that flows from the fire that continues to mix air without further chemical reactions?

The correct answer is smoke, which refers to the complex mixture of gases, particulate matter, and aerosolized liquids produced when material undergoes combustion. Smoke represents the residual product of burning materials, which contain a combination of various gases including carbon monoxide, carbon dioxide, and unburned hydrocarbons, along with solid particles and liquid droplets.

As the gas stream flows away from the fire, it can mix with surrounding air but does not undergo further significant chemical reactions beyond what has already occurred during combustion. This ongoing mixing contributes to the dispersion of smoke in the atmosphere, impacting air quality and visibility.

Other options, such as steam, vapor, and aerosol, represent different states or types of substances that don't align with the characteristics of smoke flowing from a fire. Steam is the gas phase of water, while vapor refers to a substance in its gas phase, and aerosol signifies a suspension of fine solid particles or liquid droplets in the air. Each of these has distinct properties and behaviors that differ fundamentally from smoke.