(N/A) The high stability of the triphenylmethyl cation is due to extensive delocalization of the positive charge through resonance.
The central carbocation is attached to three phenyl rings. The positive charge on the central carbon atom can be delocalized into each of the three benzene rings.
For each benzene ring,the positive charge can be delocalized to the $ortho$- and $para$-positions,resulting in three resonance structures per ring.
Including the original structure,there are a total of $10$ resonance structures ($1$ original + $3 \times 3 = 9$ resonance-contributed structures). This extensive resonance stabilization significantly lowers the energy of the cation,making it highly stable.