Here are the corrections for the underlined words or phrases:

26. **A** - It should be "interest in" instead of "interest".

27. **B** - It should be "has retired" if referring to the present situation. The sentence structure should be "My father retired three years ago."

28. **C** - It should be "so much time" instead of "so many time."

29. **D** - The sentence is correct as is; however, if there is an intended contradiction, it should be revised to maintain coherence.

30. **B** - It should be "not to" instead of "don’t".

So, the corrections are:
- 26: A
- 27: B
- 28: C
- 30: B