题目内容：
根据以下材料回答题：Genetically Modified Foods
If you want to spark a heated debate at a dinner party, bring up the topic of genetically modified foods. For many people, the concept of genetically altered, high-tech crop production raises all kinds of environmental, healthy, safety and ethical questions. Particularly in countries with long grain traditions-and vocal green lobbies--the idea seems against nature.
In fact, genetically modified foods are already very much a part of out lives. A third of the corn and more than half the soybeans and cotton grown in the U.S. last year were the product of biotechnology, according to the Department of Agriculture. More than 65 million acres of genetically modified crops will be planted in the U.S. this year. The genetic genie ( 妖怪 ) is out of the bottle.
Yet there are clearly some very real issues that need to be resolved. Like any new product entering the food chain, genetically modified foods must be subjected to rigorous testing. In wealthy countries, the debate about biotech is tempered by the fact that we have a rich array of foods to choose from and a supply that far exceeds our needs. In developing countries desperate to feed fast-growing and underfed populations, the issue is simpler and much more urgent: Do the benefits of biotech outweigh the risks? The statistics on population growth and hunger are disturbing. Last year the world's population reached 6 billion. The U. N. estimates that nearly 800 million people around the world are undernourished. The effects are devastating. About 400 million women of child-bearing age are iron deficient, which means their babies are exposed to various birth defects. As many as 100 million children suffer from vitamin A deficiency, a leading cause of blindness.
How can biotech help? Biotechnologists have developed genetically modified rice that is fortified with beta-carotene-which the body converts into vitamin A and additional iron, and they are working on other kinds of nutritionally improved crops. Biotech can also improve farming productivity in places where food shortages are caused by crop damage attributable to pests, drought, poor soil and crop viruses, bacteria or fungi.
What's the passage mainly about? A．The world's food problems.
B．The new advancement in biotech.
C．The characteristics of genetically modified foods.
D．How biotech can help solve the world's food problems.
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