Chemistry - GOC Question with Solution | TestHub

Removing ${\mathrm{H}}_1$ gives an allylic carbanion :

Removing ${\mathrm{H}}_2$ gives an ordinary carbanion :

The allylic anion is resonance-stabilised : the negative charge is shared between two carbons. The other anion carries its charge on one carbon only. The more stable conjugate base comes from ${\mathrm{H}}_1$, so the allylic proton ${\mathrm{H}}_1$ is more acidic.