Question

hydrogen fuel cells are a promising source of energy. which of these is the \waste\ product produced by a hydrogen fuel cell? helium silver argon water

Explanation:

Hydrogen fuel cells work by combining hydrogen and oxygen. The chemical reaction in a hydrogen fuel cell is \(2H_2 + O_2
ightarrow2H_2O\). So the waste product (or by - product) is water. Helium, silver, and argon are not produced in the reaction of a hydrogen fuel cell.

Answer:

water