People who have spent a lot of time in contact with animals often develop animal-induced allergies, a significant percentage of which are quite serious. In a survey of current employees in major zoos, about 30 percent had animal-induced allergies. However, a zoo employee who develops a serious animal-induced allergy is very likely to switch to some other occupation.重点在结论：有这种过敏症状的动物园员工会被调换工作。即：从事其他工作的人里面掺杂了这些感染了过敏症的动物园员工。 E：Among members of the general population who have spent as much time with animals as zoo employees typically have, the percentage with animal-induced allergies is significantly more than 30 percent.两点内容：1）其他人如果和动物园员工接触动物的时间一样长（这个assumption够严谨，即接触时间一样，要感染谁都感染，管他是动物园员工还是自己家养动物的人啊呵呵） 2）这些人感染过敏的比例大于30%。 So，因为动物园感染的员工被调职到其他occupation(工作，职业），在感染几率一样的前提下，由于得病的员工的加入，members of the general population感染比例肯定大于30%啦～～ | 
