Based on the passage provided, here are the answers to your questions:

41. **Which can be the topic of the passage?**
- **A. Villagers across the country.**

42. **Which activity is NOT MENTIONED as a way for villagers to earn their living?**
- **B. Fishing.**

43. **Why do Southern villagers need to build their houses on stilts?**
- **A. To protect the house from being attacked by wild animals.** (This is likely the correct choice based on context.)

44. **Which sentence is NOT TRUE according to the passage?**
- **B. Houses in the Southern part of Vietnam often collapse.** (This is a common example of not being true.)

45. **Which explanation has the closest meaning to the word "studious" in the passage?**
- **A. spending a lot of time studying.**

Feel free to ask if you need more clarifications or help!