
Answer
Classification of Colloidal Systems
Humidity is water vapour in air, representing a liquid-in-gas system.
Alloys are homogeneous metallic mixtures, classified as solid-in-solid solutions.
Amalgams contain liquid mercury dissolved in a solid metal, giving liquid-in-solid dispersions.
Smoke comprises fine solid particles suspended in air, hence it is a solid-in-gas system.
Correct sequence: A–II, B–I, C–IV, D–III
