24. Whose (whose and which are valid, but which doesn't fit the meaning)
25. That (referring to things, that is for a restricted clause, which is for non-restricted clause)
26. Why (the reason ...)
27. To whom (talking in)
28. In that (believe in, same reason as No.25)
29. Whom (that and which are not valid)
30. Which (same reason as No.25)
31. Susan, whose (other options are grammatically wrong)
32. You gave (short form of "that you gave")
33. That we found (same reason as 25)
34. Phoning (this is reduced relative clause, A, B, and D options are grammatical wrong). 
This sentence is kind of awkward, by the way.
35. That (same reason as No.25)
36. For which (waiting for, same reason as No.25)
37. I had (short form of "that I had")
38. Which ( same reason as No.25)
39. Whom (most relevant option)
40. "empty" (who and whom are not for the item, where is for the place)

Good luck!
:)