OFFICIAL EXPLANATION



THE PROMPT

• The word so is involved in a few idioms. So X that Y is the most common.
→ So [adjective] that ....
→ So X that Y is an idiom of consequence.
→ That is, the word so emphasizes the degree of the adjective [X] in order to present a result of that intensity.
Correct: The cookies tasted so good that I ate five of them.
Correct: The defense was so effective that the jury took only an hour to deliberate and pronounce the defendant "not guilty."

• At the least, look for options in which so is coupled with a that-clause (that + subject + verb)

• without the word that, this so in the prompt deepens the intensity of the word much, which in turn describes coverage
→ This usage of is colloquial. In this usage, so deepens the intensity of an adjective or noun but is not followed by a that-clause.
The absence of a that-clause is not likely to be seen on the GMAT.
Similar example, highly suspect: That bridge took so long to fix, creating traffic jams for months.

• I have never seen the word so used colloquially in this manner

• so that
You will also see so that, used most often to describe purpose.
→ Correct: The special ops soldier grew his beard so that he would fit in with the local male population.

• Meaning? The comet received a lot of media attention. As a result, when the comet returned in 1997, it became one of the most highly observed astronomical bodies of all time.

THE OPTIONS

• this colloquial usage of so is not seen on the GMAT
→ after the first part of the sentence (in the nonunderlined portion), we should see a that clause.
No that-clause exists.

• the adjective, highest, should be the superlative adverb, most highly
→ observed is a verb. Adjectives such as highest do not modify verbs. Ever.
→ most highly observed is the correct construction
ELIMINATE A


• this colloquial usage of so is not seen on the GMAT
→ as in option A, in this context, so should be paired with that
• same as option A: highest observed should be most highly observed
ELIMINATE B


• again, we need a that to be paired with so
• highest is incorrect (see options A and B)
ELIMINATE C


• I see no errors
• So X that Y: The comet received so much media covered that it became XYZ
KEEP

• Just as in options A, B, and C, the colloquial usage of "so" (to emphasize the intensity of a noun or adjective) is almost certainly wrong on the GMAT
• Compare to D, which uses So X that Y, a clear causal connection idiom. Option D is better
ELIMINATE E

The answer is D.

COMMENTS

I am always glad to see "veterans" whom I haven't seen in awhile as well as those who visit more frequently.

These answers contain a range of good explanations.
A few assertions are incorrect, but otherwise, good work.

The Hale-Bopp comet received so much media attention coverage when it returned in 1997, becoming one of the highest observed astronomical bodies in history.

A) when it returned in 1997, becoming one of the highest observed -> We have "received" and "returned" in parallel. "It" refers to HB comet. Further, "Becoming....." is modifying, "when HB comet retuned in 1997", It doesn't make sense. So, Becoming (-ing) modifier is incorrect.

B) when returning in 1997 to become one of the highest observed -> "when returning" is incorrect.

C) upon its 1997 return and became one of the highest observed -> "upon its 1997 return.." is incorrect.

D) when it returned in 1997 that it became one of the most highly observed -> HB comet received so much media attention coverage that it became one of...It makes sense. Let's keep it.

E) on its return in 1997, thus becoming one of the most highly observed -> "thus becoming" is incorrect.

So, I think D.

The Hale-Bopp comet received so much media attention coverage when it returned in 1997, becoming one of the highest observed astronomical bodies in history.

A) when it returned in 1997, becoming one of the highest observed
Here becoming is used as an adjective that is not required. As per the meaning, verb is necessary.

B) when returning in 1997 to become one of the highest observed
Infinative verb conveys wrong meaning

C) upon its 1997 return and became one of the highest observed
Both activites are not parallel but dependant on each other

D) when it returned in 1997 that it became one of the most highly observed
No remarks

E) on its return in 1997, thus becoming one of the most highly observed
Same as A

IMO D
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The Hale-Bopp comet received so much media attention coverage when it returned in 1997, becoming one of the highest observed astronomical bodies in history.

A) when it returned in 1997, becoming one of the highest observed
'becoming one of the highest observed...' is an incorrect phrase when describing magnitude of views on an event.

B) when returning in 1997 to become one of the highest observed
'to become' signals intent. The Hale-Bopp is not a living thing, so it is nonsensical to suggest that it has intent.

C) upon its 1997 return and became one of the highest observed
1997 return is nonsensical. This is suppose to be a date, but it seems like 1997 is modifying return. Out.

D) when it returned in 1997 that it became one of the most highly observed
This looks fine.

E) on its return in 1997, thus becoming one of the most highly observed
received so much attention 'on its return' is ungramattical. 'When it returned' is much better.

The Hale-Bopp comet received so much media attention coverage when it returned in 1997, becoming one of the highest observed astronomical bodies in history.

The correct idiom is "so ADJ ... that" to emphasize the extent of ADJ.

The comet received SO MUCH media attention coverage THAT...

Only option D uses 'that'

Choice D is the answer.

The Hale-Bopp comet received so much media attention coverage when it returned in 1997, becoming one of the highest observed astronomical bodies in history.

A) when it returned in 1997, becoming one of the highest observed // "highest observed" sounds awkward.

B) when returning in 1997 to become one of the highest observed // "highest observed" sounds awkward. to become??? A comet does not have a brain to do something intentionally.

C) upon its 1997 return and became one of the highest observed // "highest observed" sounds awkward. Also these two instances seem to be as a result of one another.

D) when it returned in 1997 that it became one of the most highly observed // so X that Y is correct. Causation is shown clearly.

E) on its return in 1997, thus becoming one of the most highly observed // verbED and verbING parallel??? Plus, "was" is missing before verbING

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Posted from my mobile device
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tyildirim92 , as usual, you are gracious. You are very welcome.

I am so thrilled for you! Congratulations and well done! You richly deserve your place.
Now go show 'em what you're made of.
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The official explanation is here.