Complex mixtures of solid and liquid particles, gases, and vapors resulting from incomplete combustion of carbon-containing materials.

• A. Dusts
• B. Vapors
• C. Fumes
• D. Smokes

Answer: (D)

When carbon-containing materials don’t burn completely, the released material becomes an aerosol called smoke. This smoke is a complex mix: tiny solid particles (like soot), liquid droplets, gases, and vapors all suspended in air. The key idea is incomplete combustion, which produces a heterogeneous mixture rather than a pure gas or pure dust.

Dusts are just solid particles from mechanical processes, not tied to burning. Vapors are gas-phase substances at room temperature, not the solid–liquid–gas cocktail produced by incomplete combustion. Fumes are fine solid particles formed when vapors condense after heating (often from metal vapors), not the broad soot-and-droplets mix from incomplete burning. The description matches smoke because it specifically describes the byproducts of incomplete combustion as a mixed aerosol.