Here are the answers for each question based on the pronunciation differences:

**Ex 1:**
1. C - strength (the other options have a different vowel sound)
2. C - yoghurt (the other options have a different vowel sound)
3. A - yoga (the other options have a different vowel length)
4. D - chip (the other options have a different vowel sound)
5. A - ingredient (the other options have a different vowel sound)
6. B - muscle (the other options have a different pronunciation)

**Ex 2:**
11. A - healthy (the other options have a different vowel sound)
12. C - mental (the other options have a different accent)
13. A - device (the other options have a different vowel sound)
14. A - replace (the other options are pronounced differently)
15. C - energy (the other options have the stress on different syllables)
16. A - asleep (the other options have a different vowel sound)
17. B - informal (the other options have different stress patterns)
18. A - provide (the other options have a different vowel sound)

**Ex 3:**
19. C - amount (the other options have a different vowel sound)
20. D - mineral (the other options have a different sound)

Feel free to reach out if you need further clarification!