In Luke 1:16-17 (RSV), the angel says to Zachariah:

"And he will turn many of the sons of Israel to the Lord their God, and he will go before him in the spirit and power of Elijah, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just, to make ready for the Lord a people prepared."

In this passage, the angel explains that John's mission is to:

1. Turn many of the sons of Israel to God (Luke 1:16).

2. Go before God in the spirit and power of Elijah (Luke 1:17), preparing the way for the Lord.

While both C and D reflect aspects of John's mission, C is the more specific part of the angel's message that answers what John will achieve directly—turning people to God. D refers to John's method or manner (going in the spirit and power of Elijah), but it does not focus on the end result of his mission, which is turning people to God.