Some have 26 vanished from the face of the earth, others are dying slowly, but all have 27 undergone changes as they have come into contact with an 28 expanding machine civilization.
2016年12月六级真题（第三套）阅读 Section A
柯林斯高阶英汉双解学习词典释义
VERB
经历；接受；遭受；忍受
If you undergo something necessary or unpleasant, it happens to you.