Sentence Correction

By comparing older ground-based observations, previous Hubble images made in 2001, and the shots taken in late 2006, astronomers have been able to study in detail what happened to the star in its dying moments.

Structure of the above sentence

<Modifier> <appositives> <subject + verb + Object>

Modifier: By comparing older ground-based observations - > it has to modify astronomers

Apposotives: previous Hubble images made in 2001, and the shots taken in late 2006, -> modifes "observations" in the preceding modifier

<subject + verb + Object> : astronomers have been able to study bla bla..

Question: To me , the sentence looks good. But I want to understand whether this should be consider the ambiguity case? that is the modifer "by comparing ...." could be modifying following appositive phrases "previous Hubble images..." .

There is nothing that allows to interpret this way except the common sense or ,may be, some logical way i can't think of. How one should treat such cases ? Help please.

By comparing older ground-based observations, previous Hubble images made in 2001, and the shots taken in late 2006, astronomers (S) have been able (V) to study in detail what happened to the star (O) in its dying moments.

I interpreted this as By comparing X, Y, and Z, <subject + verb + Object>.

@GMATMadeEasy, coming to your view,

Modifier: By comparing older ground-based observations - > it has to modify astronomers

---> AGREE

Appositives: previous Hubble images made in 2001, and the shots taken in late 2006, -> modifes "observations" in the preceding modifier

I unable to figure out that how these two are apositives?

As per my understanding, I think appositives act as synonyms of each other and in this case I don't see any such thing because of usage of AND.

Moreover, I see older ground-based observationsand previous Hubble images made in 2001
as appositives here.

Please correct me.

After focussing on the usage of COMMA before AND.

I think that older ground-based observations, previous Hubble images made in 2001 are appositives and the COMMA before AND belongs to the appositive modifier making the sentence as under,

By comparing X,Y, and Z, astronomers ....

where,

X and Y are appositive modifiers
and Z is list that contains two elements as either X and Z or Y and Z.

Please correct incase I am wrong.

By comparing X,Y, and Z, astronomers ....

I could understand only the above part .

@Bublii :

As per my understanding, I think appositives act as synonyms of each other and in this case I don't see any such thing because of usage of AND.

Replace "synonyms" with "equivalent" and u get the right definition. You dont need comma and And rule to figure this out here.

Hi Ron,

Thanks for sharing your inputs for the sentence.

I am confused with the usage of comma + and.

I have summarized my understand in the post below,

couldy you please review it and correct/add information to it?

https://www.beatthegmat.com/and-followed ... 82257.html

AIM GMAT wrote:

By comparing X,Y, and Z, astronomers ....

I could understand only the above part .

The above sentence that I wrote is based on my understanding of usage of COMMA and AND which I have summarized in the post whose link is provided above.

Please refer to that post and you will understand what I meant with it.

oops, i completely messed up here . Yeah, I see the structure and how "and " is used as well. Thanks Ron.

@bubbliiiiiiii: Manhattan SC 4th edition , Chapter 10 , Page 189 onwards nicely explains your question for AND. In case, if you have not looked at it before. If already did so, I leave you get it clarified from experts.

GMATMadeEasy, thanks for your valuable input on this topic.

I have reviewed the material and updated my summarized post so that anyone in future sees the post should gain from it.

I like this post

By comparing older ground-based observations, previous Hubble images made in 2001, and the shots taken in late 2006, astronomers have been able to study in detail what happened to the star in its dying moments.


The part in green is a complete modifier, modifying the main clause in ORANGE color....and the part in blue is modifying Observations...

Regarding COMMA + AND thing... COMMA is not assigned to AND here...its actually the modifier
"previous Hubble images made in 2001" quoted in COMMAS

Hi Atul,

I have a doubt on this part of yours

"previous Hubble images made in 2001" quoted in COMMAS

to which part is this particular modifier modifying in the sentence.............

aspirant2011 wrote:Hi Atul,

I have a doubt on this part of yours

"previous Hubble images made in 2001" quoted in COMMAS

to which part is this particular modifier modifying in the sentence.............

Hi

"previous Hubble images made in 2001" this part is actually connected to "By comparing older ground-based observations" this part...

I show u, for ex: (THIS EX IS A MADE UP SO PLEASE BARE ME FOR GRAMMATICAL MISTAKES IF ANY)

By selling Gold, a precious metal, and diamond, a precious stone, Sachin bought a new house.

Now, here Sachin bought a new house by selling WHAT ????

Ans: By selling Gold and Diamond

"a precious metal" and "a precious stone" are actually u can say sub-modifiers or NON-ESSENTIAL MODIFIERS, modifying the parts of MAIN MODIFIER

MAIN MODIFIER: By selling Gold and diamond

Why this is main modifier??? because it is modifying the main clause, its an ESSENTIAL MODIFIER.

So in the given example:

By comparing older ground-based observations, previous Hubble images made in 2001, and the shots taken in late 2006, astronomers have been able to study in detail what happened to the star in its dying moments.

The part in GREEN, combined is actually the Essential Modifier and part in Blue is Sub or Non-essential modifier...you can chop the part in blue and then u get the clarity.

Hope this help!!!