Just as listening to Franklin D. Roosevelt's famous fireside chats hel

co relative conjunction just as .... so
IMO D;
so reading Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife


Just as listening to Franklin D. Roosevelt's famous fireside chats helps students of history understand the 1930s, an era marked by incredible domestic economic distress and unparalleled foreign conflict, [url]so Abraham Lincoln's famous Second Inaugural Address helps students grasp the immense strife and challenge America faced in the post-Civil War era.
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(A) so Abraham Lincoln's famous Second Inaugural Address helps students grasp the immense strife and challenge America faced in the post-Civil War era.
(B) Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife.
(C) reading Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife
(D) so reading Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife
(E) so reading Abraham Lincoln's famous Second Inaugural Address helps students grasp a time of immense domestic challenge and strife--the post-Civil War era

Pure play of idiom and parallelism
Answer is D for completing the idiom 'as X' with another 'so Y' and matching listening to FDR's with reading Lincoln's …
The final clincher for D is the parallelism between the non-underlined "the 1930's - an era marked by" and "the post-Civil War era", a time of immense domestic challenge …"

MEANING: JUST AS listening to FDR's chats helps them understand the 1930s, SO reading Lincoln's inaugural address helps them grasp the post-Civil war era, [absolute modifier] a time of immense strife.

NOTES: Idiom is Just as X, SO (TOO) Y; the elements must be parallel.

Ans (D)

The right answer is D.

Meaning: Just as listening helps students understand the 1930s, so reading helps students grasp the post-Civil War era.
Two splits can help to solve this question.
Split #1: we are comparing the 1930s with something. Should be the post-Civil War era, the immense strife and challenge America faced?
Split#2: The right usage of the idiom just as X so Y.

Split #1: The 1930s is structurally parallel to the post-Civil War era. The 1930s is an era or period in the past and so was the post-Civil War era. Hence, it is logical to compare the 1930's with an era, being the post-Civil War era. Based on this, we can eliminate A.
Split#2: The right usage of the idiom is just as X so Y. X and Y must be parallel. Based on this, we can eliminate B and C. A can also be eliminated because listening is not parallel to Abraham Lincoln's.

Between D and E, D is better because there is a direct comparison between the 1930s and the post-Civil War era, with a time of immense domestic challenge and strife as the non-essential modifier. The non-essential modifier, however, is what is given precedence in E and this is not right. We can eliminate E and keep D as the best answer.

Just as listening to Franklin D. Roosevelt's famous fireside chats helps students of history understand the 1930s, an era marked by incredible domestic economic distress and unparalleled foreign conflict, so Abraham Lincoln's famous Second Inaugural Address helps students grasp the immense strife and challenge America faced in the post-Civil War era.

(A) so [reading]Abraham Lincoln's famous Second Inaugural Address helps students grasp the immense strife and challenge America faced in the post-Civil War era.
(B) Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife.
(C) reading Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife
(D) so reading Abraham Lincoln's famous Second Inaugural Address helps students grasp the post-Civil War era, a time of immense domestic challenge and strife
(E) so reading Abraham Lincoln's famous Second Inaugural Address helps students grasp a time of immense domestic challenge and strife--the post-Civil War era

just as...so.. tested. eliminate b&c
A is wrong because of the wrong comparison
between d&e..e is wrong because of meaning.
IMO D

OFFICIAL EXPLANATION

This sentence is built around the comparative idiom just as x, so y. As with any other comparative idiom, the two parts being compared (i.e., x and y) must be grammatically parallel.

In the original sentence, x (listening to Franklin D. Roosevelt's famous fireside chats) is not parallel to y (Abraham Lincoln's famous Second Inaugural Address). These two elements can be made parallel by changing y to reading Abraham Lincoln's famous Second Inaugural Address. Notice the parallelism with the new paragraph structure:
listening to Franklin D. Roosevelt's famous fireside chats
reading Abraham Lincoln's famous Second Inaugural Address

The sentence could be made more parallel by re-writing the immense strife and challenge America faced in the post-Civil War era to match the format of the non-underlined portion (the 1930s, an era...). In other words, for these two sections to be parallel, the time period should come first followed by a description of that time period. Notice the parallelism with the new paragraph structure:
the 1930s, an era marked by incredible domestic economic distress
the post-Civil War era, a time of immense domestic challenge and strife.

A. The idiom just as x, so y does not compare parallel elements; the description of the 1930s is not parallel to the description of post-Civil War America

B. The idiom just as x, so y is broken as the word so is omitted; parallel elements are not compared in that listening to Franklin D. Roosevelt's famous fireside chats is compared to Abraham Lincoln's famous Second Inaugural Address;

C. The idiom just as x, so y is broken as the word so is omitted

D. The idiom just as x, so y is properly maintained; parallel elements are compared in both x (listening...) and y (reading...) and in the description of the 1930s (domestic economic distress) and the post-Civil War era (domestic challenge and strife)

E. The description of the 1930s is not parallel to the description of post-Civil War America