Answer:
Hydrogen reacts with oxygen to produce water, which releases energy.
Step-by-step explanation:
In any fuel cell chemical bonds are formed and energy is released . It is a redox reaction . Bond energy is converted into electrical energy.
In the given option , first option is not possible because methane reacts with oxygen to give carbon dioxide and water .
third and fourth option are ruled out because chemical reactions are using energy . No energy is released . so they are not possible.