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(单选题)What will be useful if there are no written records? (单选题)Why people can’t know much about the central Africa 200 year (单选题)The author wrote the first paragraph to ______. (单选题)What do Dr Chris Idzikowski’s words mean in the last paragra (单选题)What kind of person’s sleep quality is influenced most? (单选题)What can we know about The Sleep Council’s survey? (单选题)What cause the “junk sleep” to teenagers? (单选题)From the passage, we can learn that ______. (单选题)The bus driver calls attention because ______. (单选题)What can we know about the first paragraph?