b
(b)In hydrogen-oxygen fuel cell following reactions take place to create potential difference between two electrodes.

\(2{H_2}_{(g)} + 4O{H^ - }_{(aq)} \to 4{H_2}{O_{(l)}} + 4{e^ - }\)

\(\underline {{O_2}_{(g)} + 2{H_2}{O_{(l)}} + 4{e^ - } \to 4O{H^ - }_{(aq)}} \)

Overall reaction \(=\,2{H_2}_{(g)} + {O_{2(g)}} \to 2{H_2}{O_{(l)}}\)

the net reaction is the same as burning (Combustion) of hydrogen to form water.