There is no percentage score for this exercise because the question is so complicated!

Please read the comments when you check your answers and try to get a "feel" for the sentences which are "correct" (sometimes, as when "who" is used instead of "whom", grammatically incorrect).

"That", for instance is difficult to judge on and yet it is so frequently used in modern English. It is perhaps worth noting that it is better only used in cases where the person or persons concerned are not personal:

All the people who live round here work in the car industry.
Most people who(m) I asked were against the project.
No-one that I know speaks Greek.

"That" may well be heard in examples like the above, in informal contexts, more frequently in object cases like the second example and with words using "any", and "some".

The practical solution (in object cases) is almost certainly to omit the pronoun completely.

N.B. Don't expect your teacher to agree with all the answers; none of the teachers (whom? who?, that?) I have consulted agree with me or with each other on the subject of pronouns in relative clauses!