I have a question regarding the "milky sap" modifier here. In answer choice A, it seems like the milky sap is the one that causes mouth sores, but in answer choice B, the meaning changes and it is now the plant that causes the mouth sores. Because of this meaning choice I selected A, could someone briefly go over why my thought process was incorrect?

Hiee , can anyone explain

In the correct ans B.

how we can use displaces as the verb to grasses ?

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Correct answer B in the sentence
About 5 million acres in the United States have been invaded by leafy spurge, a herbaceous plant from Eurasia, with milky sap, that gives mouth sores to cattle and displaces grasses and other cattle food, rendering rangeland worthless.

Manas1212 , both of your examples are correct.

I think that you are suggesting that we should use logic to figure out
the most likely subject (and causal culprit);
in your examples, the logical culprit is a particular kind of mosquito,
and whether we add the "sting" does not change the causal logic.

In the prompt, the most likely culprit is some hideous plant called "leafy splurge."
What invaded the U.S.? Leafy splurge.
What is likely to be the cause of worthless rangeland? Whatever invaded the U.S.

If you are asking a different question or I have missed your point,
tag me again.
Nice work! +1


(And I just caught an error in my answers: I need to use splurge, the plant's name, not plant.
Plant is in the appositive.)

In this case, the clause beginning with "that" is a relative clause that modifies "a herbaceous plant from Eurasia." This relative clause has a subject, "that," which clearly goes with the verbs "gives" and "displaces," just as the the noun "plant" does in the following clause. The plant gives mouth sores to cattle and displaces grasses.

So, while repeating "that" would not make the sentence clearly incorrect, there is no need to repeat "that."

So, when do we have to repeat "that"? We have to repeat "that" when the meaning that we want to convey would not be effectively conveyed unless "that" were repeated.

Consider the following sentences.

I told John that I had seen a man peering into the windows of the building and that the man had been wearing a blue hat.

I told John that I had seen a man peering into the windows of the building, and the man had been wearing a blue hat.

These two sentences are pretty similar, but mean different things.

The first conveys that I told John two things, that I had seen a man and that the man had been wearing a blue hat.

The second contains only one "that," and so, it conveys that I told John one thing, that I had seen a man, and it conveys that, in addition to my telling John about the man, the man had been wearing a blue hat. Because the second "that" is not included, the sentence does not convey that I told John that the man was wearing a blue hat.

Either version is correct, but they convey different things. So, if you want to convey that I told John two things, you have to use "that" twice.

Overall, it helps to realize that analyzing parallel structures tends to be more about considering logic and effectiveness of expression than about checking to see whether a structure is constructed according to some rule.

I have a doubt in this question.

About 5 million acres in the United States have been invaded by leafy spurge, "a herbaceous plant from Eurasia with milky sap that gives mouth sores to cattle", displacing grasses and other cattle food and rendering rangeland worthless.

Isn't the quoted part a non-essential part of the sentence as it describes something on the spurge. Because if it is,then, the comma before and after the non essential can be erased with the non-essential modifier itself, giving rise to the following statement

About 5 million acres in the United States have been invaded by leafy spurge displacing grasses and other cattle food and rendering rangeland worthless.

Where displacing is modifying spurge.

I also a a doubt that the non-essential is more than a phrase because of verb "gives" is present in it

Hello sevenplusplus,

I would be glad to help you resolve your doubt.

Let's take a look at the original sentence:

About 5 million acres in the United States have been invaded by leafy spurge, a herbaceous plant from Eurasia with milky sap that gives mouth sores to cattle, displacing grasses and other cattle food and rendering rangeland worthless.

(Blue = subject, Green = verb, Pink = comma + verb-ing modifiers)

Let's understand what the sentence intends to convey. The sentence states that in the US, some 5 million acres of land have been invaded leafy spurge. Describing the leafy spurge, the sentence states that it's a plant from Eurasia. It has milky sap that gives mouth sores to cattle. This leafy spurge displaces grasses and other cattle food and renders rangeland worthless.

However, the way this sentence is worded, it suggests that because leafy spurge gives mouth sores to cattle, it displaces grasses and other cattle food and has rendered rangeland worthless.

We get this illogical meaning from the sentence because of the incorrect usage of the comma + verb-ing modifiers* displacing and rendering.

The comma + verb-ing modifier must modify the preceding action logically and must also make sense with the doer of the modified action.

In this official sentence, the comma + verb-ing modifiers displacing and rendering illogically modifies the preceding action gives by presenting the result of this action. Grasses and other cattle food are not displaced and rangeland are not rendered worthless because leafy spurge gives mouth sores to cattle.

This is the reason why Choice A is incorrect.

From the context of the sentence, we can understand that because leafy spurge displaces grasses and other cattle food, rangeland are rendered useless. So we do have this logical cause-and-effect in the sentence that must be communicated in correct grammar.

Let's evaluate Choice B now:

About 5 million acres in the United States have been invaded by leafy spurge, a herbaceous plant from Eurasia, with milky sap, that gives mouth sores to cattle and displaces grasses and other cattle food, rendering rangeland worthless.

This choice correctly conveys the logical intended meaning. The comma + verb-ing modifier displacing has been turned to simple present tense verb displaces. The comma + verb-ing modifier rendering correctly modifies the preceding action displaces, presenting the result of this action. Because the leafy spurge displaces grasses and other cattle food, it renders rangeland worthless.

*The correct usage of comma + verb-ing has been covered in great details and with pertinent examples in our SC course, In fact, this concept features in the Free Trail course offered by e-GMAT. You can register for free at e-gmat.com and review the concept.


Hope this helps.
Thanks.
Shraddha