Here are the words whose underlined part is pronounced differently from that of the others in each group:

1. C. southern (The "ou" in southern is pronounced differently than the others.)
2. A. aching (The "a" in aching has a different vowel sound than the others.)
3. A. news (The "ew" in news is pronounced differently than the others.)
4. C. lifestyles (The "y" in lifestyles has a different sound than the others.)
5. D. placed (The "ed" in placed is pronounced like /t/, while the others are pronounced /d/.)
6. D. Relative (The "re" in relative is pronounced differently from the others.)
7. C. directory (The "i" in directory is pronounced differently from the others.)
8. C. chemistry (The "ch" in chemistry is pronounced differently from the others.)
9. D. massage (The "a" in massage is pronounced differently from the others.)
10. C. nation (The "a" in nation is pronounced differently from the others.)
11. C. nurses (The "u" in nurses is pronounced differently than in the others.)
12. A. persuit (The "u" in persuit is pronounced differently than in the others.)
13. D. lazy (The "a" in lazy is pronounced differently than in the others.)
14. C. hour (The "h" is silent in hour, making its pronunciation different from the others.)
15. A. laugh (The "augh" in laugh is pronounced differently than the others.)
16. A. sleep (The vowel sound in sleep is pronounced differently than in the others.)
17. A. headache (The "ea" in headache is pronounced differently than in the others.)
18. B. should (The "ou" in should is pronounced differently than in the others.)
19. C. visited (The "ed" in visited is pronounced differently from the others.)

Feel free to ask if you need any further clarifications!