the correct use of [main subject][second noun][-ing modifier]

Question

Hi i am really confused about this construction

, which is very common in SC . and there is no definate way to deal with it !! When we have a main subject of the main sentence , then along the sentence there is a noun , then we modify this noun by -ing . sometimes OG deals with this as not clear , because the -ing modifier can refer to the first noun . sometimes it is OK , sometimes what we want is to modify the main subject ,so we use -ing W so my question : What is the rule here ? the present participle at the end of the sentence , should refer to which noun ? examples from OG 2017: please first go to the question and see official explanation : 751 about-5-million-acres-in-the-united-states-have-been-invaded-by-leafy-242544.html Displacing grasses appears illogically to modify either about 5 million acres in the United States or that gives mouth sores to cattle. so here : -ing modifier seem to modify either the main subject (acres ) or the second noun and we should eliminate that option because it is not clear that the -ing modifies . 757 to-map-earth-s-interior-geologists-use-a-network-of-seismometers-to-206347.html here we used -ing to modify the waves ( the second noun ) but following the rule of the previous question, i would argue that this is unclear , it may be refering to the main subject of the sentence (geologists) 753 the-32-species-that-make-up-the-dolphin-family-are-closely-9155.html here , we want to modify the second noun , so we avoid -ing modifier and we choose which Official explanation : Changing the verb to the participial growing introduces ambiguity, because it could refer back to the subject of the sentence (32 species) so it follows the first question's rule again . and in this question : qotd-over-the-next-few-years-251503.html?fl=notifications#p2074359 robbing in the correct answer modifies the whole action ( demands for river water may change the saline content of the bay)

EducationAisle · Answer

That's not the reason we should eliminate that option. The reason to eliminate the options using participial phrase is that there is no reason to use participial phrase. The leafy spurge has two  distinct  (and entirely unrelated) effects:
i) it gives mouth sores to cattle
ii) it displaces grasses and other cattle food

So, there is no reason to use the participial phrase  displacing .

On the other hand, displacement of grasses and other cattle is rendering rangeland worthless. Hence, the sentence uses participial phrase  rendering .

Don't believe any explanation is needed here now, since this case is not really a  violation  of the rule of the previous question.

Actually here, there is only one clause

The 32 species include the animal known as the killer whale, growing up ...

So, it is very clear that participial phrase  growing up...  illogically modifies  32 species .

foryearss · Answer

Thank you for explanation ,following the rule that -ing always modifies the subject of the previous sentence , everything is clear now except 
751

the OG eliminted A because -ing is ambiguous to which noun it refers ( i have copied OG explanation)
lets talk about A 
About 5 million acres have been
invaded by leafy spurge, a herbaceous plant from
Eurasia with milky sap that gives mouth sores to cattle,
displacing grasses

so what is the sentence preceding displacing ? 
 a herbaceous plant from Eurasia with milky sap that gives mouth sores to cattle
What is the subject of this sentence ? a herbaceous plant
so when we say : displacing what do we mean ? we should only mean the subject of the previous sentence without any ambiguity , however : here is the OG explanation: 
Displacing grasses appears illogically to
modify either about 5 million acres in the
United States or that gives mouth sores to
cattle

following the rule that -ing only modifies the subject of the previous sentence , this should be clear that we mean a herbaceous plant NOT 5 million acres . so that explanation for me is not consistent with the rule.

foryearss · Answer

Oh god ! again
777
https://gmatclub.com/forum/before-1988- ... 41547.html
Before 1988, insurance companies in California were
free to charge whatever rates the market would bear,
needing no approval from regulators before raising
rates.

here : needing should modify the subject of the previous sentence
the market is the subject of the previous sentence , not companies (which is the subject of the main sentence)
and yet it is considered right that -ing modifies the subject of the main sentence in this construction
[main subject][second noun][-ing modifier]

EducationAisle · Answer

Hi foryearss , don't panic. Together, we will sort out everything

The thing about OG explanations is that the explanations give broad directions. For example, when the explanation says: Displacing grasses appears illogically to modify either about 5 million acres in the United States or that gives mouth sores to cattle It could basically mean that there is really no reason why displacing should be modifying either 5 million acres or milky sap . As I mentioned in my last post, the use of displacing is just incorrect here. Technically speaking, whatever rates the market would bear is just used as an object (of to charge ). So, the sentence needs to be read as: Insurance companies in California were free to charge , needing no approval from regulators before raising rates. Now, hopefully it is clear that needing would modify Insurance companies .

foryearss · Answer

Thank you very much
i have been analysing OG questoins and concluded the following :

,( please correct me if i am wrong ):

1.if we intend to modify the second noun > best thing is to use which
and which always modify the previous noun .

2. or use -ing after the noun (without a comma)
3. if we want to tell what the second noun did , best option is to make the second noun a subject to a relative clause and insert a verb : (link them with that or another relative word )
[second noun] that [verb]
a verb is better than -ing if we want to convey action done by the noun
(like 751 )
4. if we intend to modify the main subject of the sentence :we can use ,-ing at the end of the sentence ( with a comma)
example
https://gmatclub.com/forum/a-mutual-fun ... 36018.html
5. if we want to tell the result of the action : use ,-ing at the end of the sentence ( with a comme )

EducationAisle · Answer

Hi foryearss , it's now my turn to say: Oh God !

If you are going to run this kind of a complex convoluted algorithm for every option for every sentence, life will not be easy my friend (and that's an understatement ). More importantly, this kind of a byzantime algorithm (that you've suggested in your post) will completely take your focus away from meaning , and you will try to fit every option in a rigid set of grammar rules. That way, you would loose the big picture (as you did in the Displacing grasses example, where you kept wondering what the participial phrase was modifying, when actually, the participial phrase was not needed at all!). Also, your repeated references to second noun is unclear to me. By second noun , do you mean: i) Noun later in the sentence Or ii) Subject of the second clause in the sentence Since we are talking about present participles preceded by a comma , I am presuming you are referring to Subject of the second clause in the sentence. However, at one point in your post, you suggest using which . which generally modifies the nearest noun (and not the Subject of the preceding clause).

the correct use of [main subject][second noun][-ing modifier]

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