Why does the Angel Gabriel call Mary 'highly favored'?

Answer 1

You refer to this passage in the first chapter of Luke's Gospel:

v.28. And the angel came in unto her, and said, Hail, [thou that art] highly favoured, the Lord [is] with thee: blessed [art] thou among women.

Mary was the one young virgin of all the virgins in Israel chosen by God to bear Jesus, the Saviour of the world - certainly favoured and blessed!

Later, when she is carrying the baby Jesus in her womb, she visits her cousin Elizabeth, who calls her, "the mother of my Lord"