Disproportionation is a type of redox reaction in which an element undergoes both oxidation and reduction simultaneously, resulting in the formation of two different oxidation states of the same element. Let's analyze each option to determine which one represents a disproportionation reaction.

a) CaF2 + H2SO4 → CaSO4 + 2HF

This equation represents a neutralization reaction between calcium fluoride (CaF2) and sulfuric acid (H2SO4). It does not involve the same element undergoing both oxidation and reduction simultaneously, so it is not a disproportionation reaction.

b) Cl2 + 2OH- → ClO- + Cl- + H2O

This equation represents the disproportionation of chlorine gas (Cl2) in the presence of hydroxide ions (OH-). Chlorine is simultaneously reduced to chloride ions (Cl-) and oxidized to hypochlorite ions (ClO-). Therefore, this reaction is a disproportionation reaction.

c) Br- + 3OCI- → BrO3- + 3Cl-

This equation represents a redox reaction between bromide ions (Br-) and hypochlorite ions (OCI-). However, it does not involve the same element undergoing both oxidation and reduction simultaneously, so it is not a disproportionation reaction.

d) HOI + 2HCl → H2O + ICl + HCl

This equation represents a redox reaction between hydriodic acid (HI) and hydrochloric acid (HCl). However, it does not involve the same element undergoing both oxidation and reduction simultaneously, so it is not a disproportionation reaction.

Therefore, the correct answer is option B: Cl2 + 2OH- → ClO- + Cl- + H2O. This equation represents a disproportionation reaction where chlorine gas is both oxidized and reduced simultaneously, forming hypochlorite ions and chloride ions.