In which of the following mixtures, particles can be seen by naked eyes?

Suspension

The correct answer is option 2. Suspension.

In a suspension, particles are large enough to be visible to the naked eye. Suspensions are heterogeneous mixtures in which solid particles are dispersed in a liquid medium. These particles are usually larger and do not remain uniformly distributed in the liquid. Over time, they tend to settle down, causing the liquid to appear cloudy or turbid, and the particles become visible to the naked eye. In contrast, true solutions and colloidal solutions have much smaller particles that are not visible without the aid of a microscope.