求解一道逻辑题

欧洋彤

Because ethylene dibromide, a chemical used to fumigate grain, was blamed for the high rate of nerve damage suffered by people who work in grain-processing plants, many such plants switched to other chemical fumigants two years ago. Since then, however, the percentage of workers at these plants who were newly diagnosed with nerve damage has not dropped significantly. Therefore, either ethylene dibromide was wrongly blamed or else the new chemicals also cause nerve damage.

Fumigate=用烟熏消毒；fumigant=熏蒸剂

Which of the following is an assumption on which the argument depends?

1. If the new chemicals cause nerve damage, the nerve damage caused would be different from any nerve damage that ethylene dibromide may cause.
   
   
2. There are no chemical fumigants that are completely safe for workers in grain-processing plants.
   
   
3. If ethylene dibromide causes nerve damage, it does not take two years or longer for that damage to become detectable.
   
   
4. Workers at grain-processing plants typically continue to work there even after being diagnosed with nerve damage.
   
   
5. Workers at grain-processing plants that still use ethylene dibromide continue to have a high rate of nerve damage.
   问一下，C取非是怎么削弱的？
   
   

Ank

感觉跟prep上有道题类似
如果新的确诊需要两年以上的时间，就是说症状潜伏期在两年以上，那么两年前换了新的chemical fumigants这两年内新出现的患病的工人就有可能是以前的那个东西引起的。
如果新的确诊在两年以内，就是说这个症状被发现在两年以内，那么就可以确定换了fumigants以后患病的工人不是以前那个东西引起的。
啊，我说的好混乱。LZ试着理解一下吧~

gracezz

换之前，说是E这个东西引起的
换之后，非但没下降还上升了；
结论说：要么错怪了E，要么是这个新东西也会引起；

就是如果E引起的病有一个潜伏期，那就还是E的问题。