参考答案：D

解析：

前文中提到 The list of ills attributable to obesity keeps growing: Last week, obese people were accused of causing global warming.（肥胖症患者被指责导致了全球变暖）

显然这是一个结论，This          (51) comes from Sheldon Jacobson of the University of Illinois, US, and a doctoral student, Laura McLay.因此D选项conclusion是最为合适的。

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