An "Open Shop" Meant That

An "open shop" meant that

A) owners could not discriminate in any way in their hiring practices.
B) owners were legally bound to keep all escape routes open, and they were fined frequently when they did not.
C) no one could be forced to join a union as a condition for working at a given company.
D) no unions were allowed on the premises.
E) workers had voted to ban all union activity from their particular workplace.