Pack 8 Q2: Based on the most recent carbon emission numbers...

To the point and conveys the meaning correctly.

Two errors here, these emissions is not referring to any thing and semi-colon is not required. - Incorrect

empty it, and no referent - Incorrect

this has no reference here, also this should be followed by noun and higher is preferred in this context. - Incorrect

empty it, and no referent and higher is preferred in this context - Incorrect

Based on the most recent carbon emission numbers, the United States emits over five billion metric tons a year, but the emissions are higher in some countries and lower in others.

A. but the emissions are higher in some countries and lower in others--- but is correctly used to show contrast , higher and lower correctly refer to countable carbon emissions numbers
B. but these emissions are higher in some countries; lower in others----------; is unnecessary as it indicates start of new sentence and here we need two parallel sentences
C. although in some countries, it is higher and in others it is lower--- pronoun IT has vague antecedent in this sentence
D. although this is more in some countries and less in others------- we are talking about carbon emission numbers so as these numbers are countable , higher and lesser are apt words to express meaning not more and less
E. although it is more than that in some countries and less than that in others------ we are talking about carbon emission numbers so as these numbers are countable , higher and lesser are apt words to express meaning not more and less

A. but the emissions are higher in some countries and lower in others -> article 'the' makes sure it is carbon emissions we are talking about. Higher/Lower correctly used to compare numbers
B. but these emissions are higher in some countries; lower in others -> ';' introduces 2 IC's or a list. None is applicable here and hence incorrect.
C. although in some countries, it is higher and in others it is lower -> It has no antecedent
D. although this is more in some countries and less in others -> 'this' is used as adjective in GMAT, here it is used as a pronoun with no antecedent; more/less should not be used to compare numbers
E. although it is more than that in some countries and less than that in others -> It has no antecedent; more/less should not be used for number comparisons

Answer -> A

Based on the most recent carbon emission numbers, the United States emits over five billion metric tons a year, but the emissions are higher in some countries and lower in others.

A. but the emissions are higher in some countries and lower in others
Based on numbers, A country emits X per year, but emissions are higher in some countries and lower in others -> Reference to what is higher and what is lower is clear because noun 'emissions' is specified. There is enough parallelism maintained while using higher and lower. Looks good, keep it.

B. but these emissions are higher in some countries; lower in others
demonstrative pronoun 'these' refer to the very specific emissions talked in the earlier part of the sentence, which is not intended.

C. although in some countries, it is higher and in others it is lower
Reference error: Here 'it' refers to carbon emission numbers or most recent carbon emission numbers which is plural and IT is requires a singular noun.
Additionally, use of Although is not the correct form of word in this situation wherein emphasis is describing the emission numbers of countries and how those numbers are placed at large compared with other countries.
Although is used to demonstrate the surprising result of one of the clauses. e.g. Although i put in the required efforts, I failed.. 'I failed' surprising result is to show after the first part of the clause "I put in the efforts'... Adding it our question, Can we say although in some countries emissions is higher, Us emits 5M tons/year. That quantity or US emitting that quantity is mentioned as a surprising factor.
But , here is used as a coordinating conjunction joining the each idea.

D. although this is more in some countries and less in others
this - demonstrative pronoun is used to refer to something that is near, Here it seem to refer the clause before although i.e US emits...But in that case, it should be used as although this <situation>. If this refers to a clause or situation or even carbon emission number, it makes second part of the sentence, after although, not logical.

E. although it is more than that in some countries and less than that in others
That is used to refer far away things. In this case could be 'carbon emission numbers' or 'most recent carbon emission numbers' . rephrasing the sentence, carbon emission numbers is more than that <carbon emission numbers> in some countries ... it creates the sub-verb agreement error and also illogical comparison. each country will have one carbon emission number not multiple to compare with

A is the best!

Official Explanation

Based on the most recent carbon emission numbers, the United States emits over five billion metric tons a year, but the emissions are higher in some countries and lower in others.

A. but the emissions are higher in some countries and lower in others
B. but these emissions are higher in some countries; lower in others
C. although in some countries, it is higher and in others it is lower
D. although this is more in some countries and less in others
E. although it is more than that in some countries and less than that in others

A review of our answer choices shows there are several options for the subject of the clause (the/these emissions, it, and this). We also have to choose between higher/lower and more/less. There is a split between “although” and “but” to start the clause.

It might be tempting to want to narrow down options by focusing on whether we should use “but” or “although,” but we should avoid that temptation. There is some subjective reasoning and opinion about the “rules” for using one over the other, and on the GMAT, we want objective reasoning.

Let’s just look at each answer choice one by one. The modifying phrase at the beginning of the non-underlined portion tells us this sentence is talking about carbon emissions, but once we know that, we can ignore that phrase and just start with the subject “the United States.”

Option A: The United States emits over five billion metric tons a year, but the emissions are higher in some countries and lower in others.
This sentence has two independent clauses joined by a coordinating conjunction (but). The subject of the second clause is “the emissions,” which refers back to carbon emissions, and it makes sense with the rest of the sentence. Emissions is a countable noun, and higher and lower are used with countable nouns. This sentence seems correct, but we still need to review the other choices.

Option B: The United States emits over five billion metric tons a year, but these emissions are higher in some countries; lower in others.
The semicolon in front of lower creates a phrase that is just a fragment. We cannot have a fragment just hanging off the end of a sentence. Also, “these” emissions makes it seem like it is specifically referring to the carbon emissions from the U.S. that are higher or lower in another country. The number of carbon emissions in the U.S. wouldn’t change from country to country. The emission of those countries could be higher than lower than those of the U.S., but the U.S. numbers won’t change. This sentence is illogical and grammatically incorrect. It cannot be the correct answer.

Option C: The United States emits over five billion metric tons a year, although in some countries, it is higher and in others it is lower.
“It” as the subject makes this sentence too vague. What is “it”? The carbon emissions of those countries, the carbon emissions of the U.S., or the number five billion? The sentence is unclear and could potentially be saying the number five billion is lower in some countries and higher than others. Five billion is five billion. This cannot be the best answer.

Option D: The United States emits over five billion metric tons a year, although this is more in some countries and less in others.
Once again, having “this” as the subject leaves us questioning what its antecedent is—the carbon emissions of those countries, the carbon emissions of the U.S., or the number five billion? The sentence is unclear and could potentially be saying the number five billion is more in some countries and less than others. Five billion is five billion. Additionally, “less” is usually used with non-countable nouns. Lower is used as a comparative with things that have levels (like carbon emissions, the temperature, water). This cannot be the best answer.

Option E: The United States emits over five billion metric tons a year, although it is more than that in some countries and less than that in others.
This answer choice uses “less” rather than “lower,” and the “it” doesn’t have a clear antecedent, which causes the same problems as we saw in Options C and D. This cannot be the best answer.

We have successfully eliminated four answer choices. Option A is the best answer.

Well done, TheNightKing! Great job breaking down each option clearly for everyone to see and study! Kudos to you!

Great work, DinoPen! You cracked the code!

You cracked the code NandishSS! Don't forget that when you switch over "more" to "higher," you also have to change "less" to "lower!" Great catch with the vague subjects/pronouns!

You cracked the code bhavya23! Great job breaking down each option and why you chose/rejected each!

Well done, shameekv1989! You cracked the code on this one! Great catch with the more/less vs. higher/lower split - hopefully that helped you narrow things down quickly!

Well done, snoep! Another great breakdown of how you tackled a tough GMAT question! Kudos to you!

Why is "these emissions" wrong? We are talking about the very specific carbon emissions at the beginning of the sentence. "The emissions" would be too vague in my opinion because it does not clearly indicate that we are comparing the carbon emissions. "The emissions" could also mean all emissions combined (CO2, Methane, Nitrous Oxide etc.), thus the comparison would be flawed.

As for the semicolon error - okay sure. But I would never catch that because the other issue seems too obvious to me.

I would be thankful for any clarification!