The dusty and sand particles present in the air is an example of

When solid particles such as dust and sand are dispersed in a gas (air), the resulting system is classified based on particle size and behaviour.

A suspension is a heterogeneous mixture in which relatively large, visible particles are dispersed in a medium. The particles in a suspension are large enough to eventually settle out under gravity and can often be seen with the naked eye. Dust and sand particles in air fit this description: they are large, they scatter light visibly, and they settle when the air is still.

The other options do not fit:

• An emulsion is a mixture of two immiscible liquids (such as oil in water). Dust in air does not involve two liquids.
• A saturated solution is a homogeneous mixture where no more solute can dissolve at a given temperature. Dust particles are not dissolved in air.
• A dispersion is a broad term for any system in which one substance is spread throughout another, but it does not specifically describe the large-particle, settling behaviour of dust and sand in air.

Because dust and sand particles are large, visible, and settle out over time, the system is best classified as a suspension.