题目内容：

Scientist Florence Wambugu works with farmers in Kenya, a country in East Africa. She helps them grow bigger and better crops. Wambugu is especially interested in finding simple ways to produce more food.

In the past ten years, Wambugu has spent much of her time studying sweet potatoes, which are an important food in her part of Kenya. A virus (病毒) kept attacking the plants. It stopped the sweet potatoes from growing well. Because of the virus, some farmers lost three quarters of their crops.

Wambugu went to war against the virus. Her research for a way to save the sweet potatoes led to a lab in St. Louis, Missouri.

The lab mainly works on genes (基因), the chemical “computer programs” found in the cells of living things. Genes tell a plant to produce pink flowers or an animal to grow black hair. Now scientists have found ways to move genes from one living thing to another. That process is called genetic engineering.

Wambugu spent three years in the lab. As a result, she created a sweet potato plant that could fight off the virus. Wambugu tested her research in Kenya, and her plants produced wonderful sweet potatoes.

That’s just the beginning, Wambugu believes. Genetically modified (转基因的) foods, she thinks, could help farmers in poor countries grow badly needed crops, thus, fewer people will go hungry.

1.The text is written mainly to _______.

A．tell us sweet potatoes are in danger of being attacked by a virus

B．introduce Wambugu’s contribution to genetic engineering

C．introduce a new way of killing plant viruses

D．tell how hard Wambugu worked in her lab for three years

2.What caused Wambugu to set up a lab in St. Louis, Missouri?

A．Her wish to save sweet potatoes in Kenya.

B．Her great interest in genetic engineering.

C．Her love for sweet potatoes.

D．Her interest in plant life.

3.The fourth paragraph mainly explains what ________ is.

A．a crop virus	B．chemical technology
C．a computer program	D．genetic engineering

4. What is Wambugu’s attitude toward “genetic engineering”?

A．It will help more hungry people.

B．It should be carefully used.

C．It has more disadvantages than disadvantages.

D．It is a too expensive technology at present.