Option : (A) Both $A$ and $R$ are true and $R$ is the correct explanation of $A$.$\mathrm{H}_2\mathrm{S}$ is less acidic than $\mathrm{H}_2$ Te. acidity depends on $\mathrm{H}-\mathrm{S}$ and $\mathrm{H}$-Te bond dissociation energy higher the bond dissociation energy. Less will be acidity.On moving down the group the size of the atom increases and ionization enthalpy decreases. This helps to dissociate the bond easily. That's why $\mathrm{H}_2\mathrm{Te}$ is more acidic than $\mathrm{H}_2\mathrm{S}$.