a) Biological Fouling
b) Chemical Fouling
c) Corrosion Fouling
d) Freezing Fouling

Answer: c
Explanation: Corrosion fouling results from a chemical reaction involving the heat exchanger surface material.Biological Fouling is due to the microorganisms present on heat transfer surfaces. Chemical fouling results from chemical reactions of fluid that causes deposition of material on the surface of the heat exchanger. Freezing fouling is seen when one of the component in hot fluid is cooled to near freezing point.