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There are some facts about sweet potatoes you probably don’t know.
First Found in American Countries
They’re in the family of plants that includes morning glories（牵牛花）and are in a different family than yams（山药）.Yams are from Africa and are more closely related to lilies（百合花）.
A5000-Year-Old Food
When Christopher Columbus arrived in American countries in the 15th century, sweet potatoes were already a main crop. He took some with him back to Spain and by the 16th century, gardens all over Europe were growing them.
A Healthy Choice
White potatoes maybe cheaper than sweet potatoes but sweet potatoes have more nutritional（营养的）value. Also, white potatoes can lead to blood sugar problem and some other health problems.
Health Facts
◆A Rich Source of Beta-Carotene(β-胡萝卜素）
This powerful Beta-Carotene gives sweet potatoes their yellow, gold, or orange coloring and changes to vitamin A in your body. It’s thought to reduce the risk of certain types of cancer and provide protection against heart disease.
◆High in Fiber（纤维）, Low in Fat
Sweet potatoes are high in fiber which is great for health. Also, they contain very little fat.
40. What can we know about sweet potatoes from the passage?
A.Sweet potatoes were first found in Africa.
B. The family of sweet potatoes includes yams.
C. Sweet potatoes are from American countries.
D.Sweet potatoes are closely related to lilies.
41. 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
42. Sweet potatoes are good to people because they are rich in .
A.fat B. vitamin A C. sugar D.Beta-Carotene
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