Which metal is more active than h2?
(1) ag (3) cu
(2) au (4) pb

Answer is (4) - Pb.

According to the reactivity series of elements

- the elements which are above the hydrogen are more reactive than hydrogen.

- the elements which are below the hydrogen are less reactive than hydrogen.

Among the given choices, only Pb is placed above the hydrogen in the reactivity series and rest are below the hydrogen.

Hence, Pb is more active than hydrogen.

3 hours because it is a decent distance.