以下是关于完成时和现在分词同用的讲解，有提到time frame，我不是很清楚，怎么判断是不是在一个time frame。如下题
Cash flows to stock and bond mutual funds have gained strength in the last two months, but fund managers have not been eager to invest the new money, instead of preferring to raise the cash levels in their portfolios at the highest level in six months.
A.have not been eager to invest the new money, instead of preferring to raise the cash levels in their portfolios at
B.have not been eager to invest the new money, instead preferring to raise the cash levels in their portfolios to
C.have not been eager at investing the new money, instead of preferring to raise the cash levels in thief portfolios to
D.were not eager to invest the new money, instead of preferring to raise the cash levels the cash levels in their portfolios at
E.were not eager at investing the new money, instead preferring to raise the cash levels in their portfolios to
本题答案选B，所以估计 preferring to raise the cash levels和 fund managers have not been eager to invest the new money就在同一个time frame。j基金管理人从过去到现在都对...没热情，然后说他们现在跟愿意...
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,
这道题的D,E。讲N们从过去到现在掌握了...，然后说现在得出一个结论。这个为什么就不在一个frame time里了？
这个点，我不是很能判断清楚~baby姐，麻烦你了啊~~~！
下面是babybearmm的原文摘录:
以上两个例子，是想说明一个很重要的concept，关于v-ing:
the v-ing action is attached to the pertinent time frame
基于此，你就能理解Ron说的：为什么要是simultaneous，或者要是immediate consequence？
就是因为必须是attached to the time frame!!!!
那么看OG12 Q21 的D/E选项：
Neuroscientists have amassed bla bla over the past 20 yrs, now drawing bla bla.
见上句的highlighting，这两个动作所在的time frames根本就不同，相当于力学里我们在A参照系里研究事件X、然后又在B参照系里研究事件Y，所以就压根不能用v-ing来表述后面那个事件，因为后面那个事件根本就CANNOT be attached to the time frame A.
这就是为什么OG说的是：
The final descriptor in present tense, now
drawing conclusions … does not fit the
opening clause, which is in present-perfect
tense (have amassed a wealth …)
而根本不是像xdf那么归纳的所谓"v-ing"不能连完成时。他们只能看到外衣，没能体察灵魂！ | 
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发表于 2012-5-14 17:32:30
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