ANS:B - aerosol

A colloidal system, in which a liquid is dispersed in gas, is called an aerosol. An aerosol is a colloidal dispersion system consisting of solid or liquid particles suspended in a gas medium. In the case of a liquid dispersed in gas, such as fog or mist, the liquid droplets are dispersed throughout the gas phase. Aerosols are commonly encountered in nature, such as mist in the atmosphere or fog in the air, as well as in various industrial and technological applications, including spray systems, inhalers, and aerosol cans. In contrast:

• A gel is a colloidal system in which a liquid is dispersed in a solid medium.
• A foam is a colloidal system in which a gas is dispersed in a liquid medium.
• An emulsion is a colloidal system in which two immiscible liquids are dispersed in each other, such as oil dispersed in water or vice versa.