Each caste would preserve its  purity  by avoiding intermarriage and not sharing food with other castes.
Castes chose not to share their food with other castes.
Castes eagerly cooperated with each other, even permitting intermarriage.
It fell to the Aztecs in 1523, and its various buildings were changed into pyramids.
I'm in Colorado.
The group is watching a movie.
A person is competing at a show
The people are gathered around the desk.
Programs' risks increase by taking on too much unverified content.