Step 1: Identify the anion:
$\text{KO}_2$ is made of $\text{K}^+$ and $\text{O}_2^-$ (superoxide).
Step 2: Share the charge:
The two oxygen atoms together carry $-1$, so each carries $-1/2$.
Step 3: Compare:
Oxide $\text{O}^{2-}$ gives $-2$ and peroxide $\text{O}_2^{2-}$ gives $-1$, so the superoxide gives $-1/2$, option (B).
Final Answer:
Oxygen in KO2 is at -1/2.
\[ \boxed{\text{(B) }-\tfrac{1}{2}} \]