1 . The event, ________ the novel is based, is of great significance in history. (用适当的词填空)

2 . He wrote many children’s books, nearly half of________ were published in the 1990s. （用适当的词填空）

3 . The United States is made up of fifty states, one of___________ is separated from the others by the Pacific Ocean. （用适当的词填空）