Which of the Half-Reactions Below Would Be Complementary,balance the Following

Multiple Choice

Which of the half-reactions below would be complementary,balance the following half-reaction,and be chemically reasonable? Br₂ → 2 Br^-

A) 2 K → 2 K⁺
B) K⁺ → K
C) K → K⁺
D) 2 K⁺ → 2 K
E) K → K⁺²