The correct answer is option 1, aerosol. Aerosols are tiny particles of solid or liquid suspended in air. These particles can be found in a variety of forms such as dust, smoke, smog, and even certain types of gases. Aerosols can be natural, like volcanic ash, or they can be created by human activities, such as industrial pollution or spray cans. It is important to note that aerosols can have significant impacts on both human health and the environment. They can contribute to air pollution and can also have effects on climate change. Understanding aerosols and their properties is crucial for studying and mitigating the impacts of air pollution and climate change.