Which of the following statements is not correct?

(a) In ${\mathrm{NF}}_3$ , nitrogen acquires ${\mathrm{\delta }}^{+}$ charge because it is less electronegative than fluorine. With positive charge on nitrogen, the lone pair of electrons are more tightly held in ${\mathrm{NF}}_3$.

(b) In guanidine, the imino $(=\mathrm{NH})\text{ nitrogen is }{\mathrm{sp}}^2$hybridised while amino ($-{\mathrm{NH}}_2$ ) is ${\mathrm{sp}}^3$ hybridised. The proton is likely to be attached to $-{\mathrm{NH}}_2$ as its nitrogen has less s-character, Actually the imino nitrogen is protonated because this leads to the stable symmetrical resonating cation with very high delocalisation energy as there are three contributing structures.

Because of the large delocalisation energy, the cation is very much stabilised leading the guanidine to act as a strong base.

(c) Ammonia involves more bonding pair-bonding pair electronic repulsion as the pairs are located near the nitrogen atom due to its more electronegative character. In ${\mathrm{NF}}_3$, F is more electronegative and thus bonding pair lies more near F leading to less electronic repulsion.

( d) The larger the s-character of a hybrid orbital of carbon, the larger electron-withdrawing (by induction) effect it has, consequently, the larger is its base-weakening effect.