OG12 021, "分词短语"-----已解决！

kingarthur00

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,


OG D explanation: The final descriptor in present tense,now drawing conclusions… does not fit the opening clause, which is in present-perfect tense
问题：为什么分词短语的时态，要和主句时态fit呢？
而且，
例：OG12 023，正确选项C中，分词短语也没有和主句的时态一样啊！
Once designed with its weight concentrated in a metal center, the discus used in track competition is nowlined with lead around the perimeter, thereby improving stability in flight and resulting in longer throws.
盼NN解答！！！

Gail小M

前一题：v-ing形式是对前面这句话的逻辑解释和延伸  修饰是整一句话
后一题：修饰的是discus

aeoluseros

umm...详细一点说就是，现在分词做伴随状语两种功能：伴随结果、伴随动作，其中伴随动作的话逻辑主语是主句主语，伴随结果的话，没有逻辑主语，修饰前面整句，作为前面整句逻辑上的顺延。
逻辑上now drawing conclusions中draw的动作发出者是Neuroscientists，这说明现在分词结构只能伴随主句动作（如果是伴随结果，则没有逻辑主语，而应该是前面一整句话的逻辑的延伸）。而前面又是现在完成时，显然amass和draw的动作无法同时发生。那么drawing conclusions就语法上就不合理了。

kingarthur00

再次非常感谢NN aeoluseros

这么晚了，仍然在“传道授业解惑”，确实佩服

kingarthur00

追问，热心斑竹 aeoluseros！

0G12-023，C选项怎么理解呢？
“once designed”---designed的主语也是discus，应该表示是对主语discus伴随动作，！但是此时的designed时态是过去式（或则是was ，总之是过去时态），而主句是is现在时----此时，伴随主语动作，但是时态不fit啊？
个人认为解释的原因如下：
（1）因为主语discus是物体而不是人，在过去和现在可以是“同类”但是不是“同一个”物体；那么时态不同一，又怎么能称为“伴随”状语呢？
or
（2）因为designed的动作发出者是题中没提到的“人类”---逻辑主语，而discus只算的上“主句主语”，所以此时可以不伴随。那once designed叫神马名字？
不懂！！！求NN aeoluseros 继续启迪！

kingarthur00

up

kingarthur00

下去查了下语法书，看了下逻辑主语定义，（2）问解决了，designed的逻辑主语还应该是discus。

剩下的问题，还请NN解答！

kingarthur00

up

kingarthur00

默默地UP~

nightingale

designed不是现在分词，不表示伴随；是过去分词，表示被动。
非谓语的几种用法：现在分词表示伴随，过去分词表示被动，不定式表目的。

整个句子补全了省略的部分就是：(The discus used in track comopetition was) once designed with its weight concentrated in a metal center, (and) the discus used in track comopetition is now lined with lead around the perimeter thereby improving stability in flight and resulting in longer throws. 括弧里的主语和be动词部分如果补上，非谓语动词designed就成了谓语动词了，因此要增加and连词。