The reason why H₂O +Cu does not proceed to a product is that
copper has a lower activity than hydrogen and cannot replace it (answer A)
Step-by-step explanation
Replacement reaction is type of a reaction in which element react with compound and take place of another element in that compound.
That is the more reactive element replaces the less reactive element from it's compound.
Since H₂ is more reactive than Cu in reactivity series therefore no reaction occur between H₂O +Cu since Cu cannot replace H₂ from its compound.