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.
what I think is that D and E are wrong cos they change the meaning in the sense that the main focus shifts from the second clause to the first. However, I don't think that "drawing " is modifying "adulthood" because present participial modifiers modify the whole preceding clause and not the touching noun. Please clarify.
You are right that D and E are wrong because they change the focus of the sentence. They are also grammatically incorrect.
In answer choice A, the phrase "are now drawing... language" is not a modifier. Instead, this phrase contains the sentence's main verb. The modifying phrase in the sentence is "having amassed... adulthood."
Let's try taking out the modifying phrase. The sentence becomes:
"Neuroscientists are now drawing solid conclusions about how the human brain grows and how babies acquire language."
This makes it easier to see why the phrase "are now drawing... language" is not a modifier.
1 Explanation