텝스 문장 오류와 문법 설명 부탁드려요

문장별로 틀린 부분이 어디인지 궁금합니다.
1. Salt from desert soil and fertilizers from nearby farms have been washed into it. This has caused the lake to become about 25% salty than the Pacific Ocean. 정답은 c라고 하는데 about이 아니라 more가 맞는 것 아닌가요?
2. He was also of the first United States president. 역사적 사실은 단순 과거로 쓰는 것 아닌가요?
3. The terminally ill, for example, attract to the false hope that trying something unconventional might save them. are attracted가 맞을까요?
4. The people who napped for half an hour during the day did better than those who stayed awake the whole day. 여기서 the whole day가 잘못된 표현인가요?
5. Her interest in animals, however, extends beyond authorial one. is extended가 맞는지 궁금합니다.
각 문장의 오류와 이유를 설명해 주시면 감사하겠습니다.