The correct options are
A Priests believed contact with kshatriyas was polluting.
C The varna system was decided by skill and not by birth.
D Vaishyas could not perform sacrifices and rituals.
Priests divided people into four varnas- Brahmins, Kshatriyas, Vaishyas and Shudras. These varnas performed different set of functions. Shudras served the other three groups and could not perform rituals. Women were often grouped with shudras and both were not allowed to study the Vedas.