(a) is the correct answer.

The angel of the Lord appeared to her and said, "You are sterile and childless, but you are going to conceive and have a son [Samson].
Judges 13:3

But the angel said to her, "Do not be afraid, Mary, you have found favor with God.  You will be with child and give birth to a son and you are to give him the name Jesus."
Luke 1:30-31