Which of the following reaction takes place at anode in hydrogen-oxygen fuel cell?

• A. (H_2+ frac{1}{2} O_2 rightarrow H_2 O )
• B. (H_2 O rightarrow H_2+ O_2 )
• C. (H_2+2OH^- rightarrow 2H_2 O+ 2e^- )
• D. (O_2+H_2 O+ 2e^- rightarrow HO_2^-+ OH^- )