Parity $P$ symmetry restored by 1 in the $1 \oplus \bar{5} \oplus 10$?

Question

In Lie Algebras in Particle Physics 2ed - From Isospin to Unified Theories (Georgi, 1999) p.283

Georgi wrote:

When we include the $1$ in the $\rm SU(5)$ Unified Theory model, we get the 16 $$1 \oplus \bar{5} \oplus 10,$$ which we can restore the Parity $P$ symmetry lost in $\rm SU(5)$ Unified Theory model.

questions

• why is the Parity P symmetry lost in $\rm SU(5)$ Unified Theory model? I meant P is lost in weak interactions in general.

• why is the Parity P symmetry restored in the 16 as $1 \oplus \bar{5} \oplus 10$?

I am confused.

This post imported from StackExchange Physics at 2020-12-01 17:42 (UTC), posted by SE-user annie marie heart