вставьте with which who that i prefer magazines designed specifically for teenagers. i love a good read. sometimes i have to read technical texts it is quite difficult. i often borrow some books from the library is just around the corner. scientists have found a book was written about eight centuries ago.

1. I prefer magazines designed specifically for teenagers (в этом предложении либо вообще ничего не ставится, либо ствавится which, НО только при наличии глагола: which are designed или which was designed, к примеру).
2. I love people with a good read.
3. Sometimes I have to read technical texts that it is quite difficult.
4. I often borrow some books from the library that is just around the corner.
5. Scientists have found that a book was written about eight centuries ago.