Seek a hilarious joke suitable for primary school students.

A: Huh? What are you doing here? I am watering the tree. Why did you water the tree? B: Because I became a little environmental defender. A: What, people like you deserve to be surrounded by small guards? B: You don't believe it? A: Not after death. B: Well, you see, this towering tree was carefully cultivated by me. Look! That canopy blocks the sun (A: I'm bragging again. I want to cure him. All the other trees are covered by the sky. No tree is thicker, taller, bigger, greener, denser, more beautiful and more ... A: Hello! B: I'm not finished yet! What are you fooling around with? Stronger, more ... Ah ... You look like you were bitten by a mad dog. What are you yelling about? Have you finished it or not? B: It's endless! Let me ask you first, when was this tree planted? Two hundred years ago! How's it going? Isn't it amazing? How old are you now? Bad luck. It is wrong to brag. A: I asked how old you are now. B: Ten ... two years old. What, twelve? Do you have superpowers? I didn't plant this tree. It belongs to my ancestors' ancestors' ancestors (A fell asleep nearby), ancestors-ancestors! A: You are scary enough. Being an environmental guardian is better than being an environmental male tiger! B: It seems that the tiger doesn't show his face, and he thinks I'm a sick cat. Tell you, I am really a small environmental protection guard, or the leader of the small environmental protection guard group! What did you say?/Sorry? I'm a little hard of hearing. Are you the director of the environmental sanitation department? Look! I thought what made you so beautiful? It's not just picking up dung and garbage. Ha ha! To tell you the truth, I am the chairman of the United Nations Health Organization. How's it going? B: What? what did you say ? I'm a little deaf, too. A: President of the United Nations Health Organization! Oh, my God! God, don't scare me to death! Your lips are empty. Who will believe you? What evidence do you have? A: Yes. B: What? A: It's a secret. Please say it! A: OK, please call me the president of the United Nations Health Organization first. B: Then I'll scream! A: Call! B: Pretending to be the president of the United Nations Health Organization. Oh, no, that's wrong. B: That's right! You are such an impostor! A: No! B: What's the reason? A: I have been forced to this point, so I can only say. B: Say it! You see, I planted 70% trees in the first-class wildlife reserve in China. Really? Really? I lied to you that you were a puppy. B: Then I'll give you a taste of your own medicine. What's the trick? B: Let me ask you something. The trees in the national first-class wildlife reserve are hundreds of years old. How old are you now? Like you, I'm ten ... two ... years old. B: give up! A: Give up. B: Besides, the president of the United Nations Health Organization has become a puppy! Extra, extra. A: It is my good wish to become the president of the United Nations Health Organization. Oh, let's stop wrangling with each other here and green our motherland with practical actions! B: Yes, this is the real little environmental defender. Qi: Starting today, we should study hard to make the future earth bluer, greener and cleaner!