11．A new study suggests that early exposure to germs（细菌） strengthens the immune（免疫的）system．That means letting children get a little dirty might be good for their health later in life．
The study involved laboratory mice．It found that adult mice raised in a germ-free environment were more likely to develop allergies．asthma and other autoimmune disorders． There are more than eighty disorders where cells that normally defend the body instead attack tissues and organs．
Richard Blumberg，who led the study，is a professor at'Harvard Medical School in Boston，Massachusetts．He says，in 1989，medical researchers who sought to explain these diseases，first discovered that the increasing use of antibacterial soaps and other products，especially early in life，could weaken immune systems．
Now，Dr．Blumberg and his team have what is the first biological evidence to link early exposure to germs to stronger adult immune systems．They say this exposure could prevent the development of some autoimmune diseases．
In the adult germ-free mice，they found that inflammation（发炎）in the lungs and colon was caused by so-called killer T cells．These normally fight infection．But they became overactive and targeted healthy tissue-an autoimmune condition seen in asthma and a disease called ulcerative colitis．
Dr，Blumberg says the mice raised in a normal environment did not have the same reaction．He says their immune systems had been"educated"by early exposure to germs．
Rates of autoimmune disorders are rising worldwide，but mostly in wealthier，industrialized countries．According to Dr．Blumberg，it might be high time that people were warned to be more careful with the early use of antibiotics（抗生素） and the prescription from their doctors．
Rob Dunn is a professor of ecology and evolutionary biology at North Carolina State University in Raleigh．He says the new study does not mean people should stop washing．"Wash your hands，but don't do it with antibacterial soap．Let your kids play in a reasonable amount of dirt and get outside and get exposed to a diversity of things"，says Rob Dunn．
71．Who first found immune systems might get harmed by overly using antibacterial products？C
A．A professor of ecology and evolutionary biology．
B．A professor at Harvard Medical School in Boston．
C．Medical researchers who tried to explain autoimmune disorders．
D．Medical researchers who tried to treat autoimmune disorders．
72．To keep healthy in the future，children had betterA．
A．play in a dirty environment once in a while
B．live in a germ-free endronrnent
C．use plenty of antibacterial soaps
D．stay in under developed countries
73．Why are germ-free mice easy to develop lung inflanunation？B
A．Because their T celh fight bacteria effectively．
B．Because their T cells attack the healthy tissues．
C．Because their lungs become abnormally active．
D．Because their lungs have weaker tissues．
74．It can be inferred from the text thatD．
A．washing hands is no longer a good habit for children
B．antibiotics will be forbidden in children's hospitals
C．exposure to dirt helps build children's character
D．the abuse of antibiotics may be condemned
75．Where does this text most probably come from？C
A．A teacher's handbook． B．A story book．
C．A science magazine． D．A travel journal．
分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了研究发现免疫系统可能会受到过度使用抗菌产品的伤害，孩子们在一个无菌环境中成长不利于他们的健康．
解答 71．C．细节理解题．根据文章第三段"He says，in 1989，medical researchers who sought to explain these diseases，first discovered that the increasing use of antibacterial soaps and other products，especially early in life，could weaken immune systems"可知试图解释自身免疫性疾病的医学研究者首先发现免疫系统可能会受到过度使用抗菌产品的伤害；故选C．
72．A．细节理解题．根据文章最后一段"Let your kids play in a reasonable amount of dirt and get outside and get exposed to a diversity of things"可知为了将来保持健康，孩子们最好偶尔在一个肮脏的环境；故选A．
73．B．细节理解题．根据文章第五段"In the adult germ-free mice，they found that inflammation（发炎）in the lungs and colon was caused by so-called killer T cells"可知无菌小鼠肺部炎症容易发炎是他们的T细胞攻击健康组织引起；故选B．
74．D．推理判断题．根据倒数第二段"it might be high time that people were warned to be more careful with the early use of antibiotics（抗生素） and the prescription from their doctors"可知滥用抗生素可能会被谴责；故选D．
75．C．主旨大意题．通读全文，可知文章主要讲了研究发现免疫系统可能会受到过度使用抗菌产品的伤害，孩子们在一个无菌环境中成长不利于他们的健康；因此文章应该出资科学杂志；故选C．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
