The Pope has ended his trip to the US with a "sermon on the mound" at America's shrine to baseball.Pope Benedict was greeted by 57,000 cheering people as he entered the Yankee Stadium in the Bronx, New York, in his bullet-proof "popemobile".He became the third pope to deliver a "sermon on the mound," so-called because the papal altar is near the spot where the pitcher throws the ball.In a reference to the clergy sex abuse scandal that has dominated his first papal visit to the US, the pontiff said faith "means not losing heart in the face of resistance, adversity and scandal".The loudest applause came when he denounced abortion, calling for protection of the rights of "the most defenseless of human beings, the unborn child in the mother's womb."Earlier, Pope Benedict paid an emotionally charged visit to Ground Zero at the site of the World Trade Center in Manhattan.He prayed for the victims and families of the al-Qaeda attack on the twin towers on September 11, 2001.The Pope met 16 relatives of people killed when the jets hit the towers and eight survivors - four World Trade Center workers and four first responders who rushed to help. Some were Catholics and kissed his ring as they told their story.He prayed: "God of peace, turn to your way of love those whose hearts and minds are consumed with hatred."