A、To laugh at the old one. B、To take pity on the old one. C、To show off its beautiful looks. D、To praise the gardener’s kindness

There was a gardener who looked after his garden with great care. To water his flowers, he used two buckets. One was a shiny and new bucket. The other was a very old and worn-out one, which had seen many years of service, but was now past its best.
    Every morning, the gardener would fill up the two buckets. Then he would carry them along the path, one on each side, to the flowerbeds. The new bucket was very proud of itself. It could carry a full bucket of water without a single drop spilled. The old bucket felt very ashamed because of its holes: before it reached the flowerbeds, much water had leaked along the path.
    Sometimes the new bucket would say, "See how capable I am! How good it is that the gardener has me to water the flowers every day! I don’t know why he still bothers with you. What a waste of space you are!"
    And all that the old bucket could say was, "I know I am not very useful, but I can only do my best. I am happy that the gardener still finds a little bit of use in me, at least."
    One day, the gardener heard that kind of conversation. After watering the flowers as usual, he said, "You both have done your work very well. Now I am going to carry you back. I want you to look carefully along the path."
    Then the two buckets did so. All along the path, they noticed, on the side where the new bucket was carried, there was just bare earth; on the other side where the old bucket was carried, there was a joyous row of wild flowers, leading all the way to the garden.
Questions 19 to 21 are based on the passage you have just heard.
19. What was the old bucket ashamed of?
20. What was the new bucket’s main purpose of making conversations with the old one?
21. Why was the old bucket still kept by the gardener?