Consider the reaction below. 2k+> 2k+ +2br- what is being reduced? only k only br2 both k and br2 neither k nor br2

only Br2.

Justification.

In  a chemical reaction the element that gains electrons experiments a reduction in its oxidation state, that is why it is said that it is reduced.

So, to know what element is being reduced you need to calculate the oxidation states of the elements involved.

Here I indicate the oxidation states of each element if the reaction putting them inside parenthesis:

Reactants side          Products side

K (0)                           K (1+)
    
Br (0)                          Br(1-)

So, K lost one electron, increasing its oxidation statefrom  0 to 1+, meaning that it is being oxidized.

And, each atom of Br gained one electron, reducing its oxidation state from 0 to 1-, meaning it is being reduced.

Therefore, the answer is that Br2 is the substance being reduced.