Roland2rule wrote:Sydney Smith, was an incorrigible optimist, and retained good humor even in his old age when he was worn down by disease.

(A). was an incorrigible optimist, and retained good humor
(B). who was an incorrigible optimist, and retaining his good humor
(C). who was an incorrigible optimist, retained his good humor
(D). being an incorrigible optimist, who retained his good humor
(E). who was an incorrigible optimist, retained good humor

OA is C
What makes option C unique and special. I don't really know, can an Expert explain, please?

What is the source Roland?

A) was an incorrigible optimist, and retained good humor
That which precedes and and that which proceeds and need not be logically parallel.

However, this (logical parallelism) is not going to be an only error in an official material.
Another issue with A is lack of his. (Again, it is highly unlikely to be an only error in an answer choice, as is the case in E).

B and D are not sentences as they lack verb.

C is better than both A and E.
The "error" in E, however, is highly unlikely to be the only problem in an incorrect answer choice in official material, as has been stated before.

Let's dive further into it-

GMAC loves making things specific as opposed to general.
One should not ignore it, especially when there is a split as is the case here. Also please note that not all splits are genuine.
Further, please note possessive pronoun in the OAs following official SCs:

Unlike computer skills or other technical skills, there is a disinclination on the part of many people to recognize the degree to which their analytical skills are weak.
(A) Unlike computer skills or other technical skills, there is a disinclination on the part of many people to recognize the degree to which their analytical skills are weak.
(B) Unlike computer skills or other technical skills, which they admit they lack, many people are disinclined to recognize that their analytical skills are weak.
(C) Unlike computer skills or other technical skills, analytical skills bring out a disinclination in many people to recognize that they are weak to a degree.
(D) Many people, willing to admit that they lack computer skills or other technical skills, are disinclined to recognize that their analytical skills are weak.
(E) Many people have a disinclination to recognize the weakness of their analytical skills while willing to admit their lack of computer skills or other technical skills.
OA D
[spoiler](D) Many people, willing to admit that they lack computer skills or other technical skills,[/spoiler] are disinclined to recognize that their analytical skills are weak

There are no legal limits, as there are for cod and haddock, on the size of monkfish that can be caught, a circumstance that contributes to their depletion through overfishing.

(A) There are no legal limits, as there are for cod and haddock, on the size of monkfish that can be caught, a circumstance that contributes to their depletion through overfishing.
(B) There are no legal limits on the size of monkfish that can be caught, unlike cod or haddock, a circumstance that contributes to depleting them because they are being overfished.
(C) There are legal limits on the size of cod and haddock that can be caught, but not for monkfish, which contributes to its depletion through overfishing.
(D) Unlike cod and haddock, there are no legal size limits on catching monkfish, which contributes to its depletion by being overfished.
(E) Unlike catching cod and haddock, there are no legal size limits on catching monkfish, contributing to their depletion because they are overfished.
OA:A
There are no legal limits, as there are for cod and haddock, on the size of monkfish that can be caught, a circumstance that contributes to their depletion through overfishing

Also please note the omission of possessive pronoun in the OA of following official SC.

India, like Italy and China, has no single dominant cuisine: Indian food comprises many different styles of cooking, with each a product of their regional influences, from the fiery vegetarian dishes of the south to the Portuguese-influenced Goan cooking of the west, to the more familiar Mogul food of the north.

(A) with each a product of their
(B) with each as a product of its
(C) each products of their
(D) each a product of
(E) each products of
OA D

Why this anamoly?
Why no possessive pronoun after of in OA?

Let's analyze the OA:
OA) India, like Italy and China, has no single dominant cuisine: Indian food comprises many different styles of cooking, each a product of regional influences.
Technial equivalent of OA) India, like Italy and China, has no single dominant cuisine: Indian food comprises many different styles of cooking, each [style] a product of regional influences.

Inserting its or their is a HUGE problem here.
If we insert its, then we have no refferent to its. The reffernt of any pronoun MUST appear in the sentence.
If we insert their, then we have a logical error.

Therefore, citation of the source of SCs that are posted is important.
The nuances that official material adheres to are just not accommodated in most of the material out there.
And, understanding these nuances is more important in an environment where 750 is the new 700.