Here are the words that have the underlined part pronounced differently:

1. **B. though**
2. **C. cough**
3. **C. cow**
4. **D. enough**
5. **D. yogurt**
6. **D. cook**
7. **C. exhibition**
8. **B. cleaned**

So, the words with differently pronounced parts are: though, cough, cow, enough, yogurt, cook, exhibition, and cleaned.