Please answer this: David was studying human history. He selected two specific eras of human history, era A and era B. Era A was before humans had invented agriculture. And, era B was after the invention of agriculture. He noticed that human societies had changed dramatically after the invention of agriculture. Which era saw lower death rate, era A or era B?
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Answer: era A

Please answer this: Two regions, region A and region B, shared a common border, a river. Region A was favorable for sulfate-reducing bacteria and nitrogen fixing bacteria, while region B was more favorable for the developement of Non-respiratory anaerobes and facultative anaerobes. Which region had less denitrification?
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Answer: region B

Please answer this: Brad and Henry were two old friends in their 70's. Brad had very high levels of cholesterol, while Henry was healthier and had normal levels of cholesterol. Which friend does not take a drug that removes cholesterol from plasma?
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Answer:
Henry