Question

A metal x dissolves both in dil hcl & dil naoh to liberate hydrogen gas

Answer 1

Only that metals can liberate Hydrogen from acid which are more reactive than hydrogen.. And reduction potential is a good method to look on reactivity. More is red pot less ll be reactivity.

Now Red pot of hydrogen is 0, so that metals can liberate hydrogen which has - ve red pot.
Here o only Cu has +ve red pot.. So it cant liberate H2.