reduction

It is not about reduction.
The metal reacts with the H2O in the aqueous solution (I think you are mentioning about aq. solution). H2 gas is formed during reaction.

The metal is possibly K or Na.

Aq. solution means a specific metal compound is dissolved in water. So the solution consists both the metal compound and water. (Dissolution is not a chemical change, H2O remains here).

This may help you understand:

CuSO4(s) + H2O(l) -> CuSO4(aq)

In addition, the solution will be displaced by K or Na when one of them is put into it (means CuSO4(aq) becomes K2SO4(aq) or Na2SO4(aq)). It is called "displacement reaction". I think you have learned that / will learn that soon!

I think the focus is the formation of hydrogen gas in this question.
Metals at high reactivity series actually can react with water in aqueous solution to form hydrogen gas, such as sodium and potassium.
Displacement reaction is out of the scope of the question.

The metal added is probably Na or K, which react vigorously with water to give hydrogen gas. In the reaction, H-O-H(O.S. of H=+1) is reduced by the metal to give H-H(O.S. of H=0).

will this happen...?
even there is a reduction...
Cu2+ should be reduced...