Bananas are one of the world’s most important food crops.They are also one of the most

Bananas are one of the world’s most important food crops.They are also one of the most valuable exports.Bananas do not grow from seeds.Instead，they grow from existing plants.Bananas are threatened by disease because all the plants on a farm are copies of each other.They all share the same genetic weaknesses.For example，the Cavendish banana is most popular in North American and European markets.However，some kinds of fungus organisms easily infect the Cavendish.Black Sigatoka disease affects the leaves of Cavendish banana plants.The disease is controlled on large farms by putting chemicals on the plant’s leaves.Farmers put anti­fungal chemicals on their crops up to once a week.

Another fungal disease is more serious.Panama disease attacks the roots of the banana plant.There is no chemical treatment for this disease.Infected plants must be destroyed.Panama disease has affected crops in Southeast Asia，Australia and South Africa.There is concern that it may spread to bananas grown in the Americas.This could threaten an important export product for Central and South America.

The International Network for the Improvement of Banana and Plantain supports research on bananas.The group has headquarters in France and other offices in the major banana­growing areas of the world.The group says that more research must be done to develop improved kinds of bananas.The group says that fungal diseases mainly affect only one kind of banana.In fact，there are five hundred different kinds of bananas.Food and Agriculture Organization of the United Nations has said that the Cavendish banana represents only 10% of world production.

The UN agency says farmers should grow different kinds of bananas.This protects against diseases that affect only one kind.Experts warn that disease may cause the Cavendish banana to disappear.This happened earlier to another popular banana because of its genetic weakness against disease.

60．What does this passage mainly tell us?

A．Bananas are the world’s most important food crops.

B．The risk to a popular banana shows the need to grow other kinds.

C．There are five hundred different kinds of bananas.

D．How to grow bananas in different countries.

61．Bananas are threatened by disease because________.

A．they grow from seeds

B．they are one of the most valuable exports

C．the only way to prevent it is to put chemicals on their leaves

D．they have genetic weaknesses against disease

62．Panama disease________.

A．doesn’t belong to fungal disease

B．affects the leaves of banana plants

C．destroys bananas more seriously than Black Sigatoka disease

D．has spread to bananas all over the world

63．We can infer from Paragraph 3 that________.

A．the center of the group is in the US

B．the Cavendish banana covers only a small part of the yield of bananas

C．the key to solving the disease is to research all kinds of bananas

D．each fungal disease affects five hundred different kinds of bananas

60．B　主旨大意题。根据全文内容和结构判断，文章主要介绍威胁Cavendish香蕉的真菌类疾病，进而显示出种植其他种类香蕉的必要性。故答案为B项。

61．D　细节理解题。根据第一段内容可知，香蕉易受病害威胁是因为其遗传上的抗病弱点。下文也有叙述。

62．C　细节理解题。根据第二段前两句可知A项错误；根据第二段第二句可知这种疾病威胁香蕉作物的根部，B项错误；根据第二段后三句可知，这种香蕉疾病已影响到东南亚、澳大利亚和南非，有可能传播到美洲，D项错误；由文章前两段分别对两种真菌病毒的描述可知，C项正确。

63．B　推理判断题。根据第三段中“The group has headquarters in France”可知其中心位于法国，A项错误；根据第三段第三句可知，应对这种疾病的办法是培育改良品种，而不是调查所有的品种，C项错误；根据第三段第四句可知D项错误；由第三段最后一句可判断B项正确。