According to some estimates, over 30 percent of the carbon dioxide emi

D) whereas just over 10 percent of the carbon dioxide emitted comes from automobiles in Japan.

Emitted where? The sentence doesn't make it clear. The meaning is ambiguous.
The sentence could mean over 10% of the carbon dioxide emitted globally comes from automobiles in Japan. Or it could simply mean over 10% of the carbon dioxide emitted in Japan comes from automobiles.

B makes the meaning clear, and thats why is the correct answer.

Hope this helps!
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Why is D incorrect?

For those who narrowed answer choice down to B or D.

B According to some estimates, over 30 percent of the carbon dioxide emitted in the United States comes from automobiles, whereas automobiles release just over 10 percent of the carbon dioxide emitted in Japan. Tenses are same and meaning is logically same

D) According to some estimates, over 30 percent of the carbon dioxide emitted in the United States comes from automobiles, whereas just over 10 percent of the carbon dioxideemitted comes from automobiles in Japan. 2 verbs out in the no where

Even I chose the wrong one

The conjunction while can be used to indicate contrast, but it can also be used to mean that two actions are parallel in time; thus, it is somewhat ambiguous as used in the original sentence. In addition, the non-underlined portion of the sentence sets up a comparison between the percentage of American carbon dioxide emissions that come from cars driven in the U.S. and the percentage of Japanese carbon dioxide emissions that come from cars driven in Japan. In the underlined portion of the original sentence, however, this comparison is lost because the phrase just over 10 percent of carbon dioxide does not clearly refer to the total amount of carbon dioxide emitted in Japan. Thus, you can eliminate Choice A. Since there is no 2/3 split, go through your remaining answer choices aiming to make your comparison parallel and logical. In addition, be on the lookout for a conjunction that is clearer than while.

In Choice B, the conjunction whereas clearly indicates a contrast, and the comparison mentioned above is parallel and logical, so keep choice B.

You can eliminate Choice C because the phrase compared to Japan renders the comparison set up in the non-underlined portion illogical and nonparallel. In addition, what the automobiles release is not specified. Choice D starts off well with the proper conjunction whereas, but the phrase just over 10 percent of the carbon dioxide emitted does not clearly refer to the total amount of carbon dioxide emitted in Japan. Thus, eliminate Choice D. Last, you can eliminate Choice E because the preposition with is an illogical connecting word and the phrase with the carbon dioxide from automobiles in Japan lacks a verb to parallel comes from in the non-underlined portion of the sentence, rendering the sentence's comparison nonparallel and illogical. In addition, the dependent clause where it is just over 10 percent does not clearly refer to the total amount of carbon dioxide emitted in Japan, so this clause does nothing to clarify the sentence's comparison. Furthermore, the pronoun it is ambiguous. Not three but four strikes against Choice E! That leaves you with Choice B, the correct answer.

10 percent of the carbon dioxide (which is) emitted comes from....

As per the meaning of the sentence we are comparing carbon dioxide emission from automobiles and also we need to show cuntrast so A & E out
In C wrong comparision wiith Japan, out. Between B & D, In D subject is missing (dependent clause) for verb emitted. B is best

Can sme one explain why D is incorrect. Logically its only D where parallelism is properly followed
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You may want to try the official question that this question is based on.
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daagh Can you please explain the difference between B and D ?

Thanks

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Dillesh
B ) whereas automobiles release just over 10 percent of the carbon dioxide emitted in Japan

Leaving aside the structural aspects of sentence construction,( probably to befuddle the audience,) B simply means automobiles account for 30% of the CO2 emission in the US, while automobiles emit just over 10% CO2 in Japan.
However, it is a different story in D.
D) whereas just over 10 percent of the carbon dioxide emitted comes from automobiles in Japan. If you read D the previous free part, you might see that it gives a misleading twist to the meaning that out of the 30% of Co2 emitted in the US, over 10% of the Co2 comes from the vehicles in Japan.
This is the real problem with D.
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In the sentence co2 emission from automobiles from Usa and japan is being compared.
After the comparison marker the thing being compared must come immediately.

According to some estimates, over 30 percent of the carbon dioxide emitted in the United States comes from automobiles, while in Japan automobiles release just over 10 percent of carbon dioxide.

A) while in Japan automobiles release just over 10 percent of carbon dioxide.

B) whereas automobiles release just over 10 percent of the carbon dioxide emitted in Japan.

C) compared to Japan, where automobiles release just over 10 percent.

D) whereas just over 10 percent of the carbon dioxide emitted comes from automobiles in Japan.

E) with the carbon dioxide from automobiles in Japan, where it is just over 10 percent.

According to some estimates, over 30 percent of the carbon dioxide emitted in the United States comes from automobiles, while in Japan automobiles release just over 10 percent of carbon dioxide.

A) while in Japan automobiles release just over 10 percent of carbon dioxide. -> It is incorrect to put Japan first in the contrast.

B) whereas automobiles release just over 10 percent of the carbon dioxide emitted in Japan. -> The 1st clause ended with Automobile and 2nd started with Automobile, it makes sense. Meaning wise, it is better also. Let's keep it.

C) compared to Japan, where automobiles release just over 10 percent. -> Same as A. Incorrect.

D) whereas just over 10 percent of the carbon dioxide emitted comes from automobiles in Japan. -> Meaning changed. If we look closely, we can see, in Japan is added in last and It lost the meaning. Incorrect.

E) with the carbon dioxide from automobiles in Japan, where it is just over 10 percent. -> with is used to give the result of preceding clause. Incorrect.

So, I think B.

[quote="nitesh181989"]Why is D incorrect?[/quohere
Here the comparision in case of D is wrong.
It says 10% of the carbon emitted comes from the automobiles in Japan. But the correct comparision would be to compare 10% of the carbon emitted in Japan comes from automobiles.
In option B it is stated clearly

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why is A incorrect? In (A) aren't we comparing "USA" to "Japan"; additionally, to me it looks like "automobiles" in (B) could be referring to USA automobiles?