On grammatical class:

zo'u
marks end of logical prenex quantifiers/topic identification and start of sentence bridi.
ce'ai
lambda variable prenex; marks the end of introduction of lambda-scope variables.
ge'ai
metasyntactic variable prenex
ke'au
relative clause prenex: assigns a variable to the object of the relative clause

In notes:

brinimikra
x1 is a part of Lojban text representing rule 'prenex' according to the first edition of the book 'The Complete Lojban Language'.