Q. Consider the following:

1. Blood
2. Milk
3. Cold Drinks

How many of the above substances are classified as colloids?
Answer: Only 1 and 2
Notes: Blood and milk are colloids; they are heterogeneous mixtures where particles do not settle and cannot be separated by ordinary filtration. Blood is a colloidal suspension of cells in plasma, and milk is an emulsion of fat in water. Cold drinks are typically true solutions, not colloids, as their ingredients are completely dissolved.