What type of mixture is characterized by particles that remain suspended?

The type of mixture characterized by particles that remain suspended is a colloid. In a colloid, the dispersed particles are larger than those found in a solution but smaller than those in a suspension, allowing them to remain evenly distributed without settling out over time. This characteristic is due to the size and interactions of the particles, which enables them to stay suspended rather than precipitating or separating from the liquid medium.

Colloids can show unique properties, such as the Tyndall effect, where light is scattered by the suspended particles, making colloidal mixtures appear cloudy. This is distinctly different from solutions, where solute particles are completely dissolved, or suspensions, where the larger particles can settle out upon standing. Emulsions, which are a specific type of colloid, typically involve mixtures of two immiscible liquids stabilized by an emulsifying agent. Therefore, the distinctive feature of a colloid is the ability of its particles to remain suspended, which is why it is the correct answer.