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A(n) __ clause should always be separated from the rest of the sentence by commas

Read the passage from sugar changed the world. but there is another story as well. information about sugar spread as human knowledge expanded, as great civilizations and cultures exchanged ideas. in fact, while sugar was the direct cause of the expansion of slavery, the global connections that sugar brought about also fostered the most powerful ideas of human freedom. how do the details in this passage support the authors’ purpose? the details about the expansion of sugar inform readers about how widespread the use of sugar was. the details about human knowledge inform readers about how humans learned about sugar. the details about ideas and global connections persuade readers that sugar’s story has multiple consequences. the details about the spread of information about sugar entertain readers with stories of travel.

(1) fire extended humans’ geographical boundaries by allowing them to travel into regions that were previously too cold to explore. (2) it also kept predators away, allowing early humans to sleep securely. (3) fire, in fact, has been a significant factor in human development and progress in many ways. (4) other obvious benefits of fire are its uses in cooking and in hunting. (5) probably even more important, however, is that learning to control fire allowed people to change the very rhythm of their lives. (6) before fire, the human daily cycle coincided with the rising and setting of the sun. (7) with fire, though, humans gained time to think and talk about the day’s events and to prepare strategies for coping with tomorrow. the sentence that expresses the main idea is: (type the number of the sentence. then click “go.”)