A A boy and his father went walking in the mountains. Suddenly the boy fell, hurt himself, and cried, “ AAAh !!! ” To his surprise, he heard the voice repeating, somewhere in the mountain, “ AAAh !!! ” Then the boy shouted, “ Who are you ? ” He received the answer, “ Who are you ? ” He got angry at the answer, so she shouted, “ Foolish ! ” He received the answer, “ Foolish ! ” He looked at his father and asked, “ What's going on ? ” The father smiled and said, “ My son, listen , ” And then he shouted to mountain, “ I love you ! ” The voice answered, “ I love you ! ” Again the man cried, “ You are the best ! ” The voice answered, “ You are the best ! ” The boy was surprised, but did not understand. Then the father explained, “People call this Echo, but really this is life. It gives you back everything you say or do. Our life is just a reflection of what we have done. If you want more love in the world, have more love in your heart. If you want to be successful, work hard. This can be used in everything in life. Life will give you back everything you have given to it.” ( )20.From the story, we know ______ .