Hydrogen gas is liberated when aluminium is treated withA) AirB) Dilute HCl (or) H2SO4C) NaOH (or) KOHD) conc. HNO3

→ Al metal is stable in dry air due to the formation of protective oxide layer on its surface.Therefore H2 gas is not liberated when Al is treated with air.→ →→ Al is passive or reluctant to the action of Conc.HNO3 due to the formation of protective oxide layer on its surface in presence of Conc.HNO3.