Which best explains why blood is considered to be a suspension?

A) It has nutrients that cannot be dissolved

b) It contains particles that can settle out.

C) It has nutrients that are dissolved in its liquid portion.

D) It contains particles that mix on a molecular level.

I think the best answer is b) : it contains particles that can settle out.

The definition of suspension is a heterogeneous (that is same in all parts) mixture that contains particles that could undergo sedimentation (settle down) - this definition is close to b). It should not matter whether those particles are nutrients (so A or C are not good answers).