What Descartes Calls the "Light of Nature

What Descartes calls the "light of nature"

A) certifies something as true because it is lighted up as so clear and distinct it cannot be doubted.
B) is the same as what is "taught by nature."
C) is known innately as revealed to us by God.
D) cannot be relied on unless it is backed up by extensive argument, going back to simples and moving in small steps to complexes.