题目内容：

Most children, even the youngest of children, are delighted to be around cats and dogs. But these pets carry plenty of germs and allergens（过敏原）,prompting researchers to ask: Are cats and dogs really safe for children？

A study finds that, contrary to many parents' fears, owning cats or dogs does not increase a child's risk of developing allergies, and in fact, may actually protect them. The study's lead author, Dr. Dennic Ownby of the Medical College of Georgia, says that even he was "very surprised" by the results. Ownby and colleagues followed more than 470 children from birth to age 6 or 7, comparing those exposed to cats and dogs during their first year of life to those who were not.

By using skin-prick tests for detecting common allergies, the researchers found that, contrary to what many doctors had been taught for years, children who had lived with a pet were not at greater risk.

Even more remarkable, children who had two or more dogs or cats had an even greater reduction, up to 77 percent, in risk of allergies. Researchers suggest this protective effect may be the result of early exposure to lots of bacteria that are carried by dogs and cats. Exposing young children to these bacteria helps" exercise" their immune systems early in life so that they're better able to resist allergic diseases later.

There's something very important in that first year of life when the immune system is developing that we can retrain it away from an allergic response, said Dr. William Davis.

    And while researchers are not encouraging parents to buy dogs or cats just to reduce a child's allergy risk, they say if a family already has one or more animals, there's no need to get rid of them.

1.Why do the researchers feel “very surprised” by the results of the study?

A．Because the results are contrary to their expectation．

B．Because so many children are playing with cats and dogs．

C．Because parents are so much worried about their children．

D．Because children with animals may develop allergies easily．

2.Compared with children who have pets，those who haven’t  ______.

A．will lose the chance to develop immune system

B．may suffer allergic diseases more often

C．will reduce the harm from bacteria

D．can keep doctors away

3.It can be inferred from the passage that ______．

A．pets are ill-treated by their owners

B．less families would like to own cats and dogs

C．keeping pets is a good way to keep children healthy

D．the results of the study can make families with pets feel at ease

4.The underlined word “it” in the fifth paragraph refers to________.

A．the early life                      

B．an allergic disease

C．immune system                   

D．something important

5.What may be the best title of the passage?

A．How to protect your kids from allergies

B．Your pets may be helping your kids

C．Bacteria do good to your kids

D．Advantages of owning pets