(单选题)

From the passage we know that ______.

A.sweet potatoes have a history of 5000 years

B.Columbus was the first to find sweet potatoes

C.white potatoes are cheaper but more valuable

D.sweet potatoes often cause health problems

参考答案：A

参考解析：

推理判断题。根据第四段“A 5000-Year-Old Food”可知红薯有5000年的历史，所以A项正确；根据第五段第一句“When Christopher Columbus arrived in American countries in the 15th century, sweet potatoes were already a main crop.”可知，当哥伦布来到美洲时，红薯已经成为一种主要作物了，可知不是哥伦布发现红薯的，所以排除B项；根据第七段第一句“White potatoes may be cheaper than sweet potatoes but sweet potatoes have more nutritional value.”可知白薯便宜一点，但是红薯更有营养，所以排除C项；根据第七段第二句“white potatoes can lead to blood sugar problem and some other health problems.”可知是白薯会导致一些健康问题，所以排除D项。故选A。

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