King David’s most important achievement was that he made Jerusalem the capital of Israel. Option C is correct.
David is described in the Hebrew Bible as the second king of the United Kingdom of Israel and Judah after Saul and Ishbaal.
King David, the “sweet singer of Israel,” reigned over Israel for nearly 40 years, from 1000 B.C. to 962 B.C. King David suceed in unifying Israel. Furthermore, he established the walled city of Jerusalem as the capital of his kingdom.