Obeying "The Law"

How do we know which "Law" we are obligated to keep: the moral law, the Mosaic, the Levitical, or the Law of Christ? [Romans 2:13, Ephesians 5:21, Galatians, James 2:8, Galatians 3:24-27, 1 Corinthians 6:13, Romans 2:17-28, Romans 8:4].