Sure! Let's analyze the stress patterns of the words in each group:

1. **A. nomadic** (second syllable stressed)
**B. generous** (first syllable stressed)
**C. colourful** (first syllable stressed)
**D. countryside** (first syllable stressed)
- **Different stress:** B. **generous**

2. **A. popular** (first syllable stressed)
**B. calculus** (first syllable stressed)
**C. beehive** (first syllable stressed)
**D. disturb** (second syllable stressed)
- **Different stress:** D. **disturb**

3. **A. harvest** (first syllable stressed)
**B. collect** (second syllable stressed)
**C. peaceful** (first syllable stressed)
**D. whisper** (first syllable stressed)
- **Different stress:** B. **collect**

4. **A. charade** (second syllable stressed)
**B. transport** (first syllable stressed)
**C. expect** (second syllable stressed)
**D. paddy** (first syllable stressed)
- **Different stress:** A. **charade**

5. **A. opportunity** (third syllable stressed)
**B. inconvenient** (third syllable stressed)
**C. facility** (second syllable stressed)
**D. optimistic** (second syllable stressed)
- **Different stress:** A. **opportunity** and B. **inconvenient** can be seen as different compared to C. and D.

**Summary:**
1. B. **generous**
2. D. **disturb**
3. B. **collect**
4. A. **charade**
5. A. **opportunity** (or B. **inconvenient**)

If you have any further questions or need additional explanation, feel free to ask!