관계대명사 that과 what 질문드려요

기초가 부족해서 잘 모르겠어요. 설명해 주시면 감사하겠습니다.
맞는 답을 고르는 문제예요.
1. (that / what) Jane needs with is a life-vest.
2. (that / what) he left for Paris is true.
3. (that / what) he left in the bus is his bag.
4. Nobody knows (that / what) he is.
5. Do you understand (that / what) he said?
6. Do you think (that / what) she is rude?
7. This is (that / what) he made.