in p.102 of Zee QFT book,
"As of this writing, it is not known whether the neutrino mass is Dirac or Majorana. We will see in chapter VII.7 that a Majorana mass for the neutrino arises naturally in the SO(10) grand unified theory."
Question: However, what Zee said is puzzling --- the neutrinos in the SO(10) grand unified theory are in the 16 dim representation of SO(10), which carries chiral charge so the neutrino cannot be a Majorana. Am I correct? I think what Zee wanted to say is really breaking SO(10) to SU(5), and make the neutrino to be singlet 1 representation in SU(5), so we can give Majorana mass ONLY to this 1 representation of SU(5).
Am I correct?