# Which is more stable out of the given carbocation?

I have read in Solomon's Fryhle that +I effect of D is more than H but here in this problem it is given that (CH3)3C+ is more stable. How is it possible when Deuterium enriches the electron density over central Carbon resulting in diminishing of + charge eventually making second structure more stable. Second explanation can be on the basis of hyperconjugation which says that -CH3 is better in showing hyperconjugation than -CD3, but WHY? Please explain.

$\ce{C-D}$ bonds are stronger. Hyperconjugation is thus more easily seen with hydrogen rather than deuterium.
To see why $\ce{C-D}$ bonds are stronger.