It Was Ethical and Legal to Acquire and Possess Slaves

It was ethical and legal to acquire and possess slaves in ancient Rome and Greece.Today,however,slavery is considered both unethical and illegal.This implies that:

A) ethics and laws can be fixed or flexible principles depending on the situation.
B) ethics are always fixed but law is always flexible.
C) neither laws nor ethics are fixed principles.
D) ethics are always flexible but law is always fixed.
E) both ethics and laws are fixed principles.