Final answer:
The divine right theory attributes the right to rule directly to God.
Step-by-step explanation:
According to the divine right theory, what gave people of royal birth the right to rule was option (a) God. The Divine Right of Kings is a doctrine that asserts that a monarch's authority to rule comes directly from God, not from the people, the will of the aristocracy, or any constitution. Monarchs are considered to be chosen by divine will, and their authority is seen as sacred and unquestionable. This concept held that the monarch acts as God's representative on Earth, and to oppose the monarch was to oppose God Himself.