1 Conan Doyle once wrote historical novels,but became popular thanks to detective stories.2 Professor black used to study deserts,and he knows a lot about the animals that live there.3 I used to read only science fiction or fairy tales, but now I love adventure literature.4 When I visited my grandmother, we were with friends.we used to play hide-and-seek in a big cave.5 What's the matter? You look upset.