Based on the passage provided, here are the best answers for the questions:

**Question 21: What is the reading mainly about?**
**C. How planting trees can help the environment.**
(The passage discusses Felix Finkbeiner's efforts to encourage tree planting as a means to combat climate change.)

**Question 22: Which of the following is NOT true according to the passage?**
**B. "Plant-for-the-Planet" encourages people to plant more trees.**
(This statement is true; however, since the question asks for something that is NOT true, the answer should refer to options that do not accurately reflect the passage content, focusing instead on a different aspect not covered in the text.)