The following text is for questions 19 to 22.

    A group of swans landed on a beach where a crow was hopping around. The crow watched the swans arrogantly.

    He came closer and said, "You fly gracelessly! All you know is how to flap your wings. Can you glide? Can you do acrobatics in the air? No, that's impossible!" He laughed. "Let's compete. I' ll show you what flying really is!"

    The swan agreed and both launched themselves into the air. They began flying. While making derisive comments on the swan's manner of flying, the crow flew around him. They kept flying and flying until the land was lost to sight and the water stretched endlessly everywhere. Slowly, the crow started to give less comments and finally stopped. He felt tired and it made it hard for him to fly. He struggled to not fall into the water.

    Seeing the tired crow that started to touch the water several times, the swan asked, "Is that another trick? Why do you keep touching the water, brother? " ·

    "No," cried the crow. He was very tired so that his desire to show off had completely gone. "I'm in trouble ... a curse on my boasting! If you are not willing to help me, I' ll drown ... "

    Looking at the crow, the swan had pity on him. Then he took the crow on his shoulder and flew back to the shore.

19. Why did the crow challenge the swans?