参考答案：B

解析： Economists say that the main spur to the global soybean boom is the emergence of a middle class in China, much of whose newly disposable income has been spent on a richer, more varied diet. Over the past decade, China has been transformed from a net exporter of soybeans to the world’s largest importer in some years of whole soybeans as well as oil and meal byproducts.因果关系的理解和判断。根据原文，文中把全球大豆畅销的原因归结为“the emergence of a middle class in China”即“中国中产阶级的出现”，而题干中却将其原因归结为“the rise in soybean production in China and its increased export of related products”即“中国大豆产量的增加和相关产品出口的增加”，显然该说法与原文不符，因此，该题的说法是错误的。 注意：掌握表因果关系的信号词，可以帮助听者做出正确的判断。原文第一句使用系表结构，直截了当说明原因。题干使用了短语attribute to(归因于)。