Which of the following is less acidic among the given halogen...

Due to stronger-I-effect of $\mathrm{F}$ than that of Cl, $\mathrm{CHF}_{3}$ should be more acidic than $\mathrm{CHCl}_{3}.$ But actually reverse is true. This is due to : $\mathrm{CCl}_{3}^{-}$ left after the removal of a proton from $\mathrm{CHCl}_{3}$ is stabilised due to presence of $d$ -orbitals in Cl than: $\mathrm{CF}_{3}^{-}$ left after the removal of a proton from $\mathrm{CHF}_{3}$ which is not stabilised due to the absence of $d$ -orbitals on $\mathrm{F}$.