Which of the following statements is not correct?

(a) For elements in the same periodic group, the larger the basic site atom the more spread out (delocalized) is the charge and the weaker is the base. Thus,${\mathrm{I}}^{-}$is a weaker base than ${\mathrm{F}}^{-}$. Alternatively, HI is stronger acid than HF, the conjugate base follows the reverse order. 

(b) ${\mathrm{H}}_2\mathrm{O}$ is a stronger acid than ${\mathrm{NH}}_3$ , thus, the conjugate base ${\mathrm{OH}}^{-}$ is weaker base than ${\mathrm{NH}}_2^{-}$

( c) Electron-attracting inductive effect of -OH decreases the electron density on N and thus decreases the basicity of $-{\mathrm{NH}}_2$ . 

(d) In ${\mathrm{Cl}}_3\mathrm{C}:$, the unshared electron pair of the carbon in the p orbital undergoes extended p-d 1t bonding into an empty d orbital of each of the three Cl atoms:

Resonance stabilization makes a more dominating role than the inductive effect, making ${\mathrm{Cl}}_3{\mathrm{C}}^{-}$weaker base than${\mathrm{F}}_3{\mathrm{C}}^{-}$. In F, there is nod orbitals, hence, no stabilization occurs in${\mathrm{F}}_3{\mathrm{C}}^{-}$.