快考了，急救这个我觉得不是夹心结构呀！！！！！！！！

36. 17. GWD25-Q17（原CD16-17）

Until recently, the Inuit people led a nomadic existence, sheltering in
  igloos, the ice-block domes that are peculiar to north-central Canada,
  and in structures made of stones, bones, driftwood, and skins.

A.      Until recently, the Inuit people led a nomadic existence, sheltering

B.       During recent times, the Inuit people lead a nomadic existence,
  sheltering

C.      In the times that are recent, the Inuit people led a nomadic existence, sheltered

D.      Up until recently, the Inuit people, leading a nomadic existence, have sheltered

E.       Until recent times, leading a nomadic existence, the Inuit people
  were sheltered

这道题目选A，关于D的错误，我看到以前有人讨论说夹心结构，可是我觉得不是啊，夹心结构一般不是分词既可以修饰前面的名词，又可以修饰后面的名词吗，请解释一下夹心结构吧， 我有点糊涂

谢谢了！积攒人品，考试好运哈！

恩，有道理，可是能跟我进一步说下夹心结构吗？