Final answer:
King Louis XVI based his authority on the Divine Right.
Step-by-step explanation:
King Louis XVI based his authority on A) Divine Right. The Divine Right of Kings is a political and religious doctrine that claims a monarch's right to rule is directly given by God and not subject to any earthly authority. This theory suggests that only God can judge an unjust king and any attempt to depose or restrict the king's powers goes against the will of God.