美国英语听力80篇1 Lesson20

（单词翻译）

[00:06.48]Lack of Vitamin¹ A is the leading cause of blindness among children in deveoping countries.
[00:14.55]These children do not get enough Vitamin A in the food they eat.
[00:21.11]In Africa,more than 3,000,000 children suffer from blindness or sickness caused by lack of Bitamin A.
[00:30.17]Scientists say sweet potatoes are rich in beta carotene--the natural orange-colored substance² that the human body needs to produce Vitamin A.
[00:43.23]One recent study found that orange-colored sweet potatoes are an excellent food for families in southern and eastern Africa.
[00:53.89]Scientists from Kenya,Uganda and the International Potato Center in Peru³ supervised⁴ the ten-year study.
[01:03.87]The scientists found that several kinds of sweet potatoes produce excellent harvests in some areas where Bitamin A deficiency⁵ is widespread⁶.
[01:16.33]They said sweet potatoes provided⁷ large amounts of Vitamin A at a very low cost.
[01:24.09]People in Africa liked the orange-colored sweet potatoes used in the study.
[01:30.72]Some people had thought Africans would not acceppt such potatoes because they are sweeter than locally-grown sweet potatoes.
[01:40.62]The traditional African sweet potato is white and contains little or no beta-carotene.
[01:48.98]However, research studies and taste tests showed the new sweet potatoes are able to compete with the local crops.
[01:58.26]Wanda Collins is a research official at the International Potato Center.
[02:04.94]She says the study found that mothers in Africa accepted the orange-colored sweet potatoes.
[02:13.15]Women who knew the value of these potatoes continued to buy them when food shortages⁸ caused price increases.
[02:22.89]Ms.Collins says the next step is to develop this important crop in other areas of Africa.
[02:32.42]The International Potato Center reports that many women and girls in southern and eastern Africa grow sweet potatoes.
[02:42.48]The crops are grown on small pieces of land used to produce family food supplies.
[02:48.96]African farmers produce almost 7;000,000 tons of sweet potatoes each year.
[02:56.51]However, the production rate is only about five tons per hectare⁹.
[03:02.36]In all developing countries, the average production rate is fifteen tons per hectare