What type of solution is characterized by having the smallest particle size and the ability to pass through filters?

A true solution is characterized by having a uniform composition and being able to pass through filters due to its very small particle size, typically less than one nanometer. In a true solution, the solute particles are so small that they cannot be seen with the naked eye and remain equally distributed throughout the solvent, which allows for clarity and the absence of sediment.

In contrast, colloids contain larger particles that do not settle out under the influence of gravity but are still larger than those in a true solution. Suspensions consist of larger particles dispersed in a fluid, which can settle over time and typically do not pass through filter paper. An emulsion is a type of colloid formed by mixing two immiscible liquids where one is dispersed in the other, and this also does not demonstrate the characteristics of a true solution. Therefore, true solutions are distinct in their ability to pass through filters and their smaller particle size, defining them clearly from the other types mentioned.