Answer:
A heterogeneous mixture that has very small dispersed particles and stays mixed for a long time is a "colloids".
Explanation:
Consider the two types of heterogeneous mixture:
Suspensions: It is a mixture of liquid and particles of a solid and the particles may be visible by naked eyes.
If left alone, solid particles will settle down and separate over time.
Colloids: It is a heterogeneous mixture in which one substance's very tiny particles are spread uniformly across another substance. Particles will not settle down over a period of time. They're going to remain suspended or float.
Therefore, according to the above definition of suspensions and colloids, it is clear that the answer to this question is Colloids.
The complete statement is: A heterogeneous mixture that has very small dispersed particles and stays mixed for a long time is a colloids.
