Concept:A metal can displace hydrogen from steam only if it is more reactive than hydrogen in the activity series.
Explanation:Iron is placed above hydrogen in the metal activity series, so it can displace hydrogen from steam.
When hot iron reacts with steam, iron oxide and hydrogen gas are produced.
The balanced chemical equation is:
3Fe+4H2O→Fe3O4+4H2Copper is below hydrogen and cannot liberate hydrogen gas.
Tin and lead are less reactive than iron and do not react with steam under normal school laboratory conditions.
Therefore, iron is the correct choice.
Answer:A. iron