题目内容：

    The research from the U.S. Centers for Disease Control and Prevention shows that food allergies ( 过 敏 ) in children have increased about 50 percent. Common symptoms  of allergic responses include itchy mouth, throat tightening, and difficulties in breathing.

Food allergy is a medical condition of exposure to certain foods. It occurs when the immune system attacks the protein in food that in normal cases is harmless. According to reports, more than 170 foods cause allergic reactions. The major food allergens are in eggs, milk, peanuts, wheat, soy, fish, tree nuts, and crustacean shellfish.

There are several reasons behind the rise in food allergies. The food being produced these days is high in sugar, unhealthy fats, genetically modifies and some food farms have  pesticides ( 农 药 ) and other food have been injected drugs. All this can have a negative impact on our microbiome (微生物群), which is the basis of good health and immunity.

In a study comparing two children, a 15-year-old who lived in urban Italy and a 14-year-old child from rural Africa, it clearly showed a significant difference in the diversity of bacteria in their guts. The reason lies in their diet. The child from rural Africa has his diet low  in fat and rich in plant-based foods which are grown and harvested locally by villagers. In contrast, the Italian kid’s diet was rich in animal protein, sugar then low in fiber. Ultimately, the microbiome of the kid from Italy was less than that of the kid from Africa.

Besides, the so-called ‘hygiene hypothesis’ suggests that decreased exposure to microbes in early life can lead to an increased chance of allergies in later life, because of individuals not having built up immunity at a young age.

Yet another reason for the explosion in allergies may be environmental changes. The environment has seen a rise in temperature and is estimated that in the coming decades the temperature could rise even further by 10 degrees. As a result of this warm climate, the growing seasons will be longer, increasing allergen count thus making allergies even worse. According to scientists, climate change is a contributing factor that needs immediate attention.

Dr. R. Sharon, researcher of Allergy and Asthma Research Centre at Stanford University, believes the cause of allergies will ultimately come down to a combination of many factors.

Food allergies have no cure but can be managed by avoiding food that brings the  reactions. Scientists are studying food allergies medical methods for general use. They are all trying to actively understand a certain part of the puzzle when it comes to allergies.

1.What can we learn from the passage?

A.Scientists have found an effective method to solve food allergies.

B.There could be many reasons that combine to lead to food allergies.

C.Environmental changes are the most important reason for food allergies.

D.To decrease children’s allergies, we should make them eat less every day.

2.In paragraph 4, the two children are mentioned to show that

A.pesticides have bad effects on people’s food

B.a person’s daily diet can affect his microbiome

C.food allergies have no cure but can be avoided

D.climate  change is another factor for food allergies

3.What is the main purpose of this passage?

A.To explain the causes of food allergies.

B.To stress the influences of food allergies.

C.To introduce the solutions to food allergies.

D.To tell people the symptoms of food allergies.

4.What’s the author’s attitude to the treatment of food allergies?

A.Indifferent. B.Positive.

C.Doubtful. D.Critical.