Sunspots, vortices of gas associated with strong electromagnetic

Hello KittyDoodles,

We hope this finds you well.

To answer your query, in Option C "although never sighted at" serves as an adverbial modifier on the clause "Sunspots...appear on the surface of the Sun as dark spots", indirectly conveying that sunspots appear on the sun's surface as dark spots, but sunspots have never been seen on the sun's poles or equators, which are parts of the sun's surface.

We hope this helps.
All the best!
Experts' Global Team

In this sentence you have two nouns, "sunspots" and "dark spots (on the surface of the sun)". These two nouns—or, more precisely, this one noun and one noun phrase—both refer to precisely the same set of visible features of our Sun.
The references are precisely identical—in other words, "if you made a Venn diagram for them, it would be one circle" (something you often hear sarcastically in political discussions, but here I'm using it literally)—because the one that appears second (dark spots...) is a detailed definition/identification of "sunspots".

Because we have two nouns that represent the same set of phenomena, you have more flexibility than usual grammatically. Any verb whose subject, as determined from context, is those things can take either of those two instances, "sunspots" or "dark spots...", as its actual grammatical subject.
If you had a "they" or "them" or "their", you could conceive of a technical ambiguity here, but that ambiguity would exist only in algebraic-type terms where two things can't be the same unless they're literally the same word. That isn't actually ambiguity (since the 'two meanings' are just one meaning), and any such pronoun would be perfectly fine.

KarishmaB

Hi Karishma,

Why can't we use verb after "although" in C?
(C) appear on the surface of the Sun as dark spots although "they are" never sighted at

I read in this https://gmatwithcj.com/articles/the-although-misconception/ that we can insert verb after although

Thanks in advance!

"Although' is a conjunction and gives a dependent clause so normally it will carry a subject and a verb. We do reduce these clauses sometimes are shown in my previous post.
Let me know if there is still some doubt.

Sighted at is not a correct idiom
B is wrong because of meaning error
C is wrong because of tense error
D is wrong because although require sub clause
E is wrong because of meaning error