新PREP的一道求帮助

yinxiaolin

188. (26379-!-item-!-188;#058&001961)
Neuroscientists, having amassed a wealth of knowledge over the past twenty years about
the brain and its development from birth to adulthood, are now drawing solid conclusions
about how the human brain grows and how babies acquire language.
A. Neuroscientists, having amassed a wealth of knowledge over the past twenty years
about the brain and its development from birth to adulthood, are
B. Neuroscientists, having amassed a wealth of knowledge about the brain and its
development from birth to adulthood over the past twenty years, and are
C. Neuroscientists amassing a wealth of knowledge about the brain and its development
from birth to adulthood over the past twenty years, and are
D. Neuroscientists have amassed a wealth of knowledge over the past twenty years about
the brain and its development from birth to adulthood,
E. Neuroscientists have amassed, over the past twenty years, a wealth of knowledge about
the brain and its development from birth to adulthood,
答案是A，可是，having不是不能做定语么？DE说drawing 容易歧义修饰前面的adulthood 想问一下 逗号+分词 是既可以做定语又可以表示功能结果吗？如果没有逗号是怎么样的呢？

yinxiaolin

自己顶 help啊~