大全465

465.     Just as plant species native to regions with browsing mammals evolved many natural anti-browser defenses (such as sharp spines and toxic chemicals), so humans in malarial regions have evolved dozens of chemical defenses against malaria.

(A) so humans in malarial regions have evolved dozens of chemical defenses against malaria

(B) humans in malarial regions have been evolving dozens of chemical defenses against malaria

(C) there has been, in malarial regions, an evolution of dozens of human chemical defenses against malaria

(D) dozens of chemical defenses against malaria have been evolved by humans in malarial regions（A）

(E) similarly, in malarial regions, humans have evolved dozens of chemical defenses against malaria

My question is: 为什么前半句是一般过去时态, 后半句是现在完成时态?　谢谢．

  Just as plant species native to regions with browsing mammals evolved many natural anti-browser defenses ,

这句话并不是用的过去时，题干参见黄色部分，后面的with结构修饰regions，browsing是形容词，evolved many natural anti-browser defenses 分词修饰 mammals；native to是复合介词。

那前面的Just as 接什么？可以不引导从句而是连一个大词组么？  窃以为，evolved是个动词。

  本句，我试着翻译一下，请指教：就好像植物习惯了地区，什么地区呢？有很多吃植物的动物的地区，这些植物进化成了有很多天然的防吃植物的动物的防御功能。    如此翻译，才能和后面的  so humans in malarial regions have evolved dozens of chemical defenses against malaria. 相比较。

所以，我也想问问时态不一致的问题。

请指教。