From my understanding, plants make oxygen via photosynthesis. Without plants, trees etc, there wouldn't be enough oxygen in the atmosphere for people or other life to survive. Once humans had evolved, we also began using wood to build houses and harvesting food. Without forests, modern humanity wouldn't exist at all
Answer
1. Reasons for migration:
✔ B
2. Economic opportunity:
✔ D
3. Tenement living:
✔ C
4. Challenges in the US:
✔ A
Between the rivers and mountains
I’m pretty sure sorry I hope you get it right
The reason why these words are often used in similar settings is because they can be connected. An example would be this: "Sometimes when people actively dissent, they are persecuted because the government has no tolerance for dissent".
I attempted to comment it here but it wouldn’t work so to see look at this doc;
https://docs.google.com/document/d/10wivXzHjMXYknW-Wjqng1PkR_iv7g2OTCknyNQqln9Q