Sentence Correction

The Chicago and Calumet Rivers originally flowed into the St. Lawrence by way of Lake Michigan, but having been redirected by constructing canals so that the water now empties into the Mississippi by way of the Illinois River.
A. Rivers originally flowed into the St. Lawrence by way of Lake Michigan, but having been redirected by constructing
B. Rivers had originally flowed into the St. Lawrence by way of Lake Michigan, but they have been redirected by constructing
C. Rivers, which originally flowed into the St. Lawrence by way of Lake Michigan but have been redirected by the construction of
D. Rivers, originally flowing into the St. Lawrence by way of Lake Michigan, but having been redirected by the construction of
E. Rivers, originally flowing into the St. Lawrence by way of Lake Michigan, have been redirected through the construction of
Source -Gmat Prep
[spoiler]How come originally flowing into the St. Lawrence by way of Lake Michigan modify Rivers ?? Isnt it an adverbial modifier (an -ing modifier coming after a comma)..In case it is then it needs a clause ...

Same issue here
https://www.manhattangmat.com/forums/min ... t6094.html

and according to Ron comma + ing setup are supposed to modify entire clause....and not phrases ..[/spoiler].

Hi Kaulnikhil,

-ing modifier typically modifies a clause, but it can also modify a noun or noun phrase. This question is a perfect example of that, and not the 1st one I see in an official Q. It's just that the GMAT prefers to use -ing introduced modifiers to modify clauses, and relative pronoun introduced modifiers (which, who, whom, whose, when, where, that...) to modify the noun or noun phrase before the comma.


A is a sentence fragment. "The rivers flowed..., but having been redirected"

B commits the verb tense error of pairing the past perfect 'had flowed' with the present perfect 'they have been redirected'

C and D are also sentence fragments.

E is correct. Much more detailed explanation can be found as this is GMATPrep Question 2237. Set topic='verb tense AND Modifers' and difficulty='600-700' in the Drill Generator to practice similar questions.

Good luck,
-Patrick

What I have realized in this case is that comma has been used before verb ing is to clarify the flowing of both the rivers.

Example:

X and Y flowing into the Z are the most important rivers of the country.

=> It means that only river Y has flown into Z.

Again,

X and Y, flowing into the Z are the most important rivers.

Experts, please comment on my thinking. We are confused about the issue of "comma + Verbing". As per OG, Comma + Verbing will modify the entire preceding clause.

Thanks in advance.

Hi Stacey,

I have a question regarding choice E). MGMT SC guide says that the tense of "V-ing" form is determined by the main verb tense of the sentence. In E), the main verb, "have", indicates the present perfect. Apparently, "flowing" cannot take the present perfect tense since the word "originally" tells us the these two rivers have stopped flowing into the St. Lawrence. Is there anything wrong with my reasoning?

Thanks a lot!

Stacey Koprince wrote:

As per OG, Comma + Verbing will modify the entire preceding clause.

This is true in the vast majority of cases - and it is true when there actually is a preceding clause.

A clause is a sequence of words that includes a conjugated verb.

In your example, there is no clause before the "comma -ing):

X and Y, flowing into the Z, are the most important rivers.

(Note: I added a second comma.) "X and Y" are the subjects - nouns - of the sentence. "Flowing into the Z" cannot modify the preceding clause because there is no preceding clause in the sentence.

In terms of whether your example without the commas means "flowing into the Z" only refers to Y and whether the example with the commas means "flowing into the Z" refers to both X and Y... honestly, if I saw the sentence without the commas, I would be confused about the meaning of that sentence. If you want to mention two rivers but only one flows into the Z, you'd want to put that info first: Y, flowing into the Z, and X are the most important rivers in the country. Now I know for sure that the "Z" info applies only to Y. If you put the Z info after the compound subject X and Y, with or without commas, then the info is ambiguous.

Thanks Stacy for the clarification.

IMO E