Sure! Here are the best answers for each of the questions:

1. **Circle the word that has the underlined part pronounced differently from the others.**
- **Answer:** D. why (The "wh" in "when," "whose," and "where" is pronounced as /w/, while the "wh" in "why" is pronounced with a long /h/ sound.)

2. **Circle the word that differs from the other three in the position of primary stress.**
- **Answer:** D. paper (The primary stress in "explain," "become," and "attract" falls on the second syllable, whereas "paper" has primary stress on the first syllable.)

3. **We have English class ________ 2 p.m. to 4.30 p.m.**
- **Answer:** C. from (The correct phrase is "from 2 p.m. to 4.30 p.m.")

4. **__________ is the nature world, where plants, animals, and people live.**
- **Answer:** B. Environment (The environment encompasses the natural world where living things exist.)

5. **You should ________ on food and medicine if you hear about a storm coming.**
- **Answer:** A. stock up (The correct phrase is "stock up on food and medicine.")

6. **People shouldn’t use plastic bags _________ they can reduce land pollution.**
- **Note:** The sentence seems incomplete. A suitable completion could be "because" or "so that." If you have a specific list of options for this question, please provide them for a more accurate answer.

Please let me know if you need further assistance!