Sir,this is what you have said in another question.my doubt is than why we require although next to subject here,when sunspots is already an implied subject in c
Quote:
On the GMAT, the implied subject of a verbless clause must be crystal clear.
For this reason:
The implied subject of COMMA + VERBLESS CLAUSE is invariably the preceding noun.
The implied subject of an INTRODUCTORY VERBLESS CLAUSE is invariably the subject of the following clause.
I have doubts about this.
What about the following sentences?

The money was transferred to the customers, as [it was] promised.
Elaine thought of a new plan while [she was] peeling potatoes.
The money was transferred to the customers, as promised.
If the intended subject of promised is the money, the GMAT likely would place as promised BEFORE the money, so it's closer to the implied subject.

Elaine thought of a new plan while [she was] peeling the potatoes.
Here, no comma precedes the verbless clause while peeling -- a different construction from the one discussed in my initial post.
When a verbless clause is not set off by a comma, the implied subject of the verbless clause is the preceding subject.
Here, the preceding subject is Elaine, so it's clear that ELAINE was PEELING the potatoes.

sagarock wrote:Sir,this is what you have said in another question.my doubt is than why we require although next to subject here,when sunspots is already an implied subject in c

As discussed in my post above, a verbless although-clause must be adjacent to its implied subject.
Consider this a rule about verbless although-clauses.

More generally:
A verbless clause should be AS CLOSE AS POSSIBLE to its implied subject.
In C, almost twenty words separate although never sighted from its implied subject sunspots.
The result is a sentence that is hard to follow.
Eliminate C.

sir as per the magoosh this statement is incorrect,but this follows verbless clause rule.
Although opposing slavery on philosophical grounds,jefferson owned plantations with several hundred slaves.

Sir .please provide your explanatioN.I am confused

Hii sir,Iam awaiting your reply.Thank you.

sagarock wrote:sir as per the magoosh this statement is incorrect,but this follows verbless clause rule.
Although opposing slavery on philosophical grounds,jefferson owned plantations with several hundred slaves.

Sir .please provide your explanatioN.I am confused

On the GMAT, a VERBless clause invariably serves to modify a main clause that is in the PRESENT TENSE.
Official examples:
Rising inventories, if not accompanied by corresponding increases in sales, can lead to production cutbacks.
Although accounting for only 5 percent of the world's population, United States citizens consume 28 percent of its nonrenewable resources.
Although eradicated in the United states, polio continues elsewhere.
Among the surest indications on Earth of sunspot cycles is believed to be the rate at which trees grow, as seen in the rings visible in the cross sections of their trunks.

In every case, the VERBless clause in red serves to modify the main clause in blue.
In every case, the main clause is in the present tense.

Since the Magoosh sentence is not in the present tense, it is not viable.