Smoke is an example of:(A) Solid dispersed in solid(B) Solid dispersed in gas(C) Solid dispersed in liquid(D) Gas dispersed in solid

Smoke is an example of (B) Solid dispersed in gas.

Explanation:
Smoke is a colloidal system, meaning it's a type of mixture where very small particles of one substance are dispersed throughout another. Specifically, smoke consists of tiny solid particles (such as carbon, ash, or dust) that are dispersed in a gas, typically air. This creates a suspension of solid particles within the gaseous medium, leading to what we observe as smoke.

Let's break down the options:
(A) Solid dispersed in solid: This refers to a solid-solid colloidal system (e.g., certain alloys). Not applicable to smoke.
(B) Solid dispersed in gas: This correctly describes smoke, where solid particles are floating in a gaseous medium.
(C) Solid dispersed in liquid: This would describe a system like a suspension of solids in a liquid, such as muddy water. Not applicable here.
(D) Gas dispersed in solid: This would describe a solid foam (e.g., pumice stone). Also not applicable to smoke.
Thus, the correct answer is (B) Solid dispersed in gas.