Sure! Here are the answers for the blanks in your sentences:

28. This is the day **when** we are supposed to submit our assignments.
29. The dog **that** chased the cat belongs to our neighbor.
30. She’s the one of the people **who** love to be the centre of attention.
31. They meet in an old house, **whose** basement has been converted into a café.
32. There are a lot of things **that** I need to buy before the trip.
33. Do you remember that nice Mr. Harry **who** came to dinner?
34. The hall **where** you’re giving your talk has a really good sound system.

If you have any more questions or need further assistance, let me know!