A Frightened Bird（在线收听）

    Once upon a time，a skilled archer called Geng Lei and the king of the state of Wei were standing at the foot of a tall tower．Looking up，they saw birds soaring in the sky．“Sire，I can bring down a bird for you by using a bow with no arrow．”said Geng Lei to the king．“Can archery achieve such a marvellous thing？”asked the king．“Yes，sire．”replied GengLei．After a little while，a wild goose appeared from the east．GengLei merely drew his bow and brought down the bird without shooting an arrow．“How come your skill could do such a wonderful thing？”asked the king．“This is a wounded bird．”said Geng Lei．“How did you know that？”asked the king．“It was flying very slowly and crying very sadly．”Geng Lei pointed out．“It flew slowly because its old wound still hurt．It cried sadly because it had lost its flock for quite some time．Its old wound had not yet healed and it was still very frightened．When it heard the sound of the bow it stretched its wings to soar up into the sky．That broke the wound and caused it to fall．”
    Exercises：
    回答下列问题：
    ①How could Geng Lei bring down a bird？
    ②How could Geng Lei tell that it was a wounded bird？
    ③What made the bird fall down？