Which one of the following is the exhaust pipe emission from Fuel Cell Electric Vehicles, powered by hydrogen?

1. A

   Hydrogen peroxide

   Hydrogen peroxide. Not the FCEV tailpipe product.

2. B

   Hydronium

   Hydronium. Aqueous H3O+, not the exhaust gas.

3. C

   Oxygen

   Oxygen. The cell consumes oxygen from air, it does not exhaust it as the product.

4. D

   Water vapour

   Water vapour. H2 + O2 in a fuel cell → electricity + H2O.

Summary. Official key is (d) water vapour. A hydrogen fuel-cell electric vehicle combines hydrogen with oxygen; the exhaust is water (vapour). Not peroxide, hydronium or oxygen.