Which of the following best describes a sol-gel colloidal system?
Butter and milk
Explanation for correct option:
A. Butter and milk
Colloids:
Butter and milk are a sol-gel colloidal system in which milk is a sol while butter is a gel type of colloidal system.
Explanation for incorrect options:
B. Blood is a colloidal suspension which means it can behave as a colloid as well as a suspension.
C. Beaten egg whites is a type of foam in which the dispersed phase is gas while the dispersion medium is liquid.
D. Paper is not considered a mixture.
Hence, the correct option is A i.e. Butter and milk.