King David called Christ Lord

Mark 12:35-37
[35]As Jesus was teaching in the Temple, he asked the question, “How can the teachers of the Law say that the Messiah will be the descendant of David?
[36]The Holy Spirit inspired David to say: ‘The Lord said to my Lord:  Sit here on my right     until I put your enemies under your feet.’
[37]David himself called him ‘Lord’; so how can the Messiah be David’s descendant?”