Question

We classify muddy water as a suspension because the particles of mud
a. are in solution.
b. cannot be filtered out.
c. settle out as the mixture stands.
d. remain suspended as the mixture stands.

Answer 1

Because the particles settle out as the mixture stands , as long as it's allowed to stand undisturbed 
A substance is classified as suspension if its particles is large enough for sedimentation, which means that it's size is significantly larger than the solution