React with Br2 & I2 Higher Question

[CheesyPeeps]

Homework Statement

Which of the following will react with Br2 but not with I2?
A OH−
B SO3 2−
C Fe2+
D Mn2+

Homework Equations

N/A

The Attempt at a Solution

The answer given in the marking scheme is C, and I can't figure out how to come to that conclusion. Is it something to do with electronegativity? London dispersion forces? My exam is tomorrow morning and I'm freaking out about this just a little...!

 

[Borek]

Redox potentials.

 

[CheesyPeeps]

Redox potentials.

Ah, that makes sense! Thank you very much