Which criteria determine whether a heterogeneous mixture is a colloid or a suspension?

This question has the next set of answer choices:

a) whether its composition is uniform and transparent

b) whether the particles do not settle for an extended period of time

c) whether the ratio of components is fixed

d) whether it can be separated into simpler substances through physical separation techniques

The answer is the option b: whether the particles do not settle for an extended period of time.

Justification:

Both colloides and suspensions are heterogeneous mixtures whose particles are larger than the particles of a solution, but the particles of a colloind are smaller than the partilces of a suspension. So, the suspensions settle faster than colloids.

Being both heterogeneous mixtures their ratios of the components are not fixed and they can be separated into simpler substances through physical separation techniques.

The criteria of uniformity and transparency are not used becasue they do not differentiate well suspensions and colloids.