Schools looking to ban cell phones may have a new excuse: a growing number of people are developing an allergy to metal in the d

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问题    Schools looking to ban cell phones may have a new excuse: a growing number of people are developing an allergy to metal in the devices. We all know that food allergies are on the rise—a study last year showed the rate at 1 per 70 children, compared with 1 in 250 in the 1970s. But at last month’s meeting of the American College of Allergy, Asthma & Immunology, allergists reported that many substances that once seemed innocuous (无害的) are now leading to allergic reactions, too.
   Allergies can develop when young bodies come into contact with a new substance, and an increasing number of kids have early exposure to tech tools and "adult" products that can lead to a lifetime of reactions. For instance, the nickel hardware often used on phone trim and faceplates can lead to red, itchy skin where the phone is pressed against the face of someone who developed a nickel allergy at a young age. It’s especially problematic for women, says Luz Fonacier, an allergist who attended the conference. Young girls are often first exposed to nickel when they get ears pierced, and therefore are more likely to develop sensitivity to the metal that can cause allergic reactions later on.
   Temporary tattoos could be another allergy trigger. They share a pigment used in hair dyes, which can lead to problems down the line. "You might have kids developing the sensitivity now, and then finding out only when they’re much older and decide to dye their hair, then have an attack, " says Fonacier.
   Foods that were once considered low risk, like pumpkin, are now causing some allergic reactions, too.
   So what’s behind all these newfangled allergens (过敏源) ? Some researchers believe that as humans live in cleaner, safer and more disease-free environments, the immune system — given less to do thanks to antibiotics—turns on substances once considered safe. Others note that children are being exposed to more and more new foods and foreign substances at earlier ages, which could up the chances of developing sensitivity. To be safe, Fonacier recommends Ihat children avoid piercing until after age 10. And it’s all just another reason to keep those cell phones and temporary tattoos away from young hands.
It is believed that in cleaner and safer environments the immune system will

选项 A、not work because of the disease factors
B、rely on antibiotics
C、attack substances once considered safe
D、function more efficiently than in the ordinary environments

答案C

解析 根据最后一段中的“…as humans live in cleaner, safer and more disease-free environments, the immune system--given less to do thanks to antibiotics--turns on substances once considered safe.”可知,当人类生活在更干净、更安全以及更不受疾病侵扰的环境中时(而抗生素的使用使得人体免疫系统要做的很少),人体的免疫系统就会开始攻击一些曾经被认为是安全的物质。据此可知,免疫系统会攻击曾被认为是安全的物质,C项正确。
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