If a molecule Y contains two carbon- carbon double bonds, then how many moles of ${\text{H}}_2$ are required for the complete hydrogenation of one mole of Y?

The correct option is A 2
One mole of hydrogen gas in presence of nickel or palladium as catalyst is required for complete hydrogenation of one mole of an unsaturated alkene with only one carbon-carbon double bond.

Since Y contains two carbon-carbon double bonds, two moles of hydrogen gas will be required for complete hydrogenation of one mole of Y.