Along the major rivers that traverse the deserts of northeast Africa

Hi the rule is:

"Either on X or on Y ( use of the preposition on the right hand side of both either and or)
On either X or Y (use of the preposition prior to either and or)"

with the same logic why should of not come before supply of water and good growing? I understand how meaning wise it would be wrong, so would this hence be an exception to the rule??

EMPOWERgmatVerbal GMATNinja

Great question, Kritisood!

The phrase "a combination of" is standing in for the word "both" in this idiom. The word "of" doesn't repeat because it's not actually part of the X in the idiom. You would still use the same idiom structure as "both X and Y" where X and Y need to be parallel. In this case, the only sentence that does this correctly is option B.

I hope that helps! Feel free to tag us at EMPOWERgmatVerbal if you have any other questions!

The combination of X and Y -- here combination is singular subject or plural subject? We can interpret it in this way also -- The combination of X and the combination of Y.
Again combination cannot happen of a single thing. The combination of X -- seems nonsense.

Please explain.

Hey there
Thank you for posting the question ? Let me try and help you out!
The Important thing first. Let’s start by looking at the intended logical meaning.

The sentence talks about the farming traditions that had suffered a lot for at least 6000 years. Since the major rivers are flowing through the deserts of northeast Africa, the Middle East, and northwest India, a fusion of good water supply and good growing conditions is found. This amalgamation helped the farming traditions to outgrow suffering.

Now see here two factors 'good water supply and good growing conditions' fuse together to make a single combination and this combination encouraged the farming techniques
A combination in this context is singular

Though combination can act as plural or singular word based on the context.
eg
Combination of red, blue, and green vs combinations of red, blue, and green.
When I say 'Combination of red, blue, and green ' it means that all three colors are mixed together to make up one new color. Here combination is singular
When I say combinations of red, blue, and green' it means that out of these three colors different mixtures of colors can be made. Either red and blue or blue and green or red and green or red, blue, and green are mixed up to make new colors. Here it is plural.

I hope this helps
Thanks
Anmol

please confirm
....and good growing conditions encouraged farming traditions that, in places, endured for 6,000 years.- CORRECT
(The child drew a square in the sand, but the ocean erased it)-OK
(I picked the items that fell down)_OK
(Teacher selected the students who played well for 2 months)OK

....and good growing conditions encouraged farming traditions that, in places, have endured for 6,000 years.- CORRECT
(The child drew a square in the sand, but the ocean has erased it)-

OK

- effect till now
(I picked the items that have fallen down)

Wrong

( the action of have fallen already completed before i picked)
(Teacher selected the students who have played well for 2 months) -

Ok

( selected happened in past but played well action effect till now )

....and good growing conditions have encouraged farming traditions that, in places, endured for 6,000 years.- Wrong
(The child have drawn a square in the sand, but the ocean erased it)-

Wrong

- doesnt make sense because erasing action happened after draw
(I have picked the items that fell down)_

Ok

because fell down action happened before picked items . the effect of picked is still now - OK
(Teacher have selected the students who played well for 2 months)-

OK

(teacher selection effect still now)

....and good growing conditions have encouraged farming traditions that, in places, have endured for 6,000 years.-

Correct?

The child HAS DRAWN a square in the sand, but the ocean HAS ERASED it.- AWKWARD- what happened first - Awkward
I have picked the items that have fallen down- awkward - action happened one after another.
Teacher has selected the students who have played well for 2 months -

OK

( selection effect till now , students have played well - effect till now)

Question:
Can a present perfect tense be used in main clause and relative clause together in a sentence?

GMATNinja @EMPOWERgmatVerbal@ChrisLele@CrackVerbalGMAT@

Regarding your question about the present perfect ("Can a present perfect tense be used in main clause and relative clause together in a sentence?"), I don't see anything inherently wrong with that. For example:

"I have witnessed many of the events that have taken place here."

That said, I can't think of a GMAT question that uses something like that in the correct answer choice (if anyone can think of one, please let us know!).

Based on your examples, it seems like you have a pretty solid grasp of the present perfect! Just remember that your job is to select the BEST answer choice out of the five available options. Looking at a single sentence (or part of a sentence) in a bubble and trying to determine whether it's "correct" or "incorrect" based on grammar "rules" is an entirely different job -- one that you'll never have to do on test day.

So if you understand why (B) is the best choice here (and I have a hunch that you do!), you've done your job.

I hope that helps!

ChrisLele In (B) if I replace "that have, in places" endured for" with "that have, in places, been enduring for", would the option still be correct?

A simple problem if we note that it is a "combination of X and Y", in which case we can eliminate choices #3, 4, and 5.

Between #1 and #2, I see in #1 that we have a "both" without a corresponding "and". Therefore, the answer is #2.

GMATNinja egmat
Can you please explain why present perfect continuous (PPC) (in option E) is incorrect. Can I not say that the action (of enduring) is still continuing. The official answer mentions that PPC in option E is grammatically correct but inappropriate. Requesting experts to explain - how the same is 'inappropriate'.

Thanks
Shubham

For starters, check out this post, if you haven't already: https://gmatclub.com/forum/along-the-ma ... l#p2265904.

Now consider these examples:

• "Tim dances." - This is a general statement about what Tim does. Is Tim dancing right at this moment? Maybe, maybe not. But dancing is something that Tim does with some regularity.
  
• "Tim is dancing." - This, on the other hand, suggests that Tim is in fact actively dancing at this moment.
  
• "Tim has been dancing since 6:00 a.m." - This suggests that Tim has been dancing nonstop since 6:00 a.m. If you take a time machine back to ANY moment in Tim's life, you'd be able to determine whether he was dancing at that particular moment. And for all of the moments between 6:00 a.m. and now, the answer to the question "Is Tim dancing?" would be, "Yes, he is."
  
• "The traditions have been enduring for 6,000 years." - This implies that if we take a time machine back to any moment between now and 6,000 years ago, we'd encounter traditions that are... enduring? What does it mean to say that a tradition IS enduring right at this moment? Can you show up in your time machine and say, "Oh yeah, see these traditions? They're definitely enduring right now!"? Not really -- "enduring" isn't an action that can get switched on and off like dancing.

And that's why "have been enduring" isn't terribly appropriate (E) -- it's a continuous verb tense for an action that's already continuous in nature.

Please do NOT read this and think, "Okay, GMATNinja is saying that you can only use the present perfect continuous tense with discrete actions, not continuous actions... got it, let me add that to my list of grammar rules." Please don't do that. This is a very subtle meaning nuance that is NOT governed by any clear rules, and by itself it's certainly not a great reason to eliminate (E).

Luckily, there are more important things to worry about, as discussed here: https://gmatclub.com/forum/along-the-ma ... l#p1108297.

I hope that helps!

I am aware that option B is the correct answer, and option E is incorrect due to the use of the expression 'of'. However, I made a mistake while attempting the question and focused on the distinction between 'have' and 'have been.' While EMPOWERgmatVerbal states that the use of the present perfect continuous tense and the idiomatic phrase 'enduring for' are acceptable, it ultimately becomes incorrect because it does not use the idiomatic structure 'combination of X and Y' correctly. On the other hand, ExpertsGlobal5 mentions that answer choice E incorrectly uses the present perfect continuous tense verb 'have been enduring' to describe an action that began in the past but continues to impact the present. I chose 'have been' because I believed these traditions started in the past and are still ongoing in the present. Can someone help clarify my doubt why this verb thing is acceptable by EMPOWERgmatVerbal but not by ExpertsGlobal5. I appreciate your assistance in advance.

Hi gauravsirohi93!

You're absolutely on track with your understanding, aligning perfectly with what we said eariler. Both "have endured" and "have been enduring" can indicate continuity from past to present, so your tense intuition was spot-on. But as we noted earlier, option (E) falls short due to the idiom "combination of X and Y" being used incorrectly. So, it's about idiom structure, not tense.