“Behold” The Greek word is idou (#2400 ἰδού), and it is used to get our attention. See commentary on Matthew 1:20 (“Look!). Although most usually translated “Look!” in the REV, in this context that may make it seem like Mary was rude to the angel, which was certainly not the case.
“I am the servant of the Lord.” The Greek word “servant” can also be translated “slave,” and in Mary’s mind that is most likely what she was saying. She acknowledged that she was the slave of God, and as His creation and willing servant, she was His to do with as He liked. This is true humble submission to the will of God.