Camus broke with Sartre in a bitter dispute over the nature of

OFFICIAL EXPLANATION

• Choice A is best

• In B, over is misused: the idiomatic form of expression is
broke . . . in , not broke . . . over,
and over should appear immediately before the issue in dispute (i.e. the nature of Stalinism)

• Choice C, wordy ( ) and imprecise, does not specify who was involved in the dispute.

• In D and E, dispute(d) about is less direct and idiomatic than dispute(d) over
Also, D is needlessly wordy and over is misused in E.

*****
COMMENTS ON THE OFFICIAL EXPLANATION

• The author is correct that (C) and (D) are "needlessly wordy."
-- Assertion without explanation is not very helpful.
-- "Wordy" should be among the last reasons we eliminate an option.

-- C) Camus broke with Sartre after there was a bitter dispute over the nature of Stalinism.

-- C is "wordy" because it introduces "there was."
Who was involved in this bitter dispute?
"There was" a dispute between which people? Maybe two friends of Camus and Sartre were having a dispute, and Sartre took one friend's side, an action that led Camus to break with Sartre.

Camus and Sartre were part of an influential group of thinkers.
Maybe their pals Merleau-Ponty and (Sartre's companion) Simone de Beauvoir had the bitter dispute.

-- Example of "wordy," explained: "after there was a bitter dispute over" is not as concise as
"in a bitter dispute over."

• Idiom? DISPUTE OVER - MEANING - CAUSAL SEQUENCE
The idiomatic construction can be gleaned (figured out on your own) from the correct meaning, which in turn can be gleaned from logic.

The difference between (A) "IN" and (B/E) "OVER" is a difference in logical meaning.

Set options A and E next to each other
A) Camus broke with Sartre in a bitter dispute over the nature of Stalinism.
E) Camus broke with Sartre over a bitter dispute about the nature of Stalinism.

Camus and Sartre were IN = were having . . .
a bitter dispute over = a bitter argument about or fight over . . . the nature of Stalinism

Camus broke with Sartre = Camus left whatever partnership, friendship, intellectual "camp," that Camus and Sartre had forged
Why did Camus leave?
A) says that Camus left in the middle of the bitter fight OVER [because of, about] the nature of Stalinism

E) says that Camus left OVER [because of, about] a bitter dispute [about, regarding] the nature of Stalinism.
E) says that Camus left because of a bitter fight (that was about the nature of Stalinism).

Let's say that Catherine (C) and James (J) are engaged to be married.
They get into a bitter dispute over J's membership in a hate organization.
J will not leave the hate organization. Catherine wants James to leave.
When C has had enough, when she cannot tolerate J's being a hate-monger any longer, she leaves.
She "breaks" with him.

In English we say, "We broke up over (because of) Big Problem X."
We do not say "We broke up over (because of) the break up."

Does she leave because they are having a dispute [over his membership in a hate organization]?
Does she leave simply because they are having a fight?

Or does she leave in the midst of the dispute, when she will not stand it any longer, because he is a supporter of hate?
If J left the organization, would Catherine "break" with him? Probably not.
The subject of the dispute is the reason she leaves.

Catherine would say to James: I am leaving because you will not stop being a hate-monger.
I am breaking up with you over the issue of your continuing participation in hate-mongering.

The dispute is not the instigator (fundamental cause) of the break. They have had the dispute for a long time.
Catherine breaks with James in or during the course of a dispute over his belief in hate-mongering.

By contrast, if I say that C broke with J OVER a bitter dispute involving his hate-mongering,
"over" functions as "because of."
What is the object of "because of"? The dispute. Not the content of the dispute, which should be the object of "because of."

Then the sentence means something different from A.
Now it seems as if C did not break with J during the dispute because of J's hate-mongering.
Rather, it seems that the dispute itself caused or instigated the break.

But that logical sequence is off.
His membership in a hate organization and his refusal to leave the organization CAUSED or instigated a dispute
during which, at some point, C broke from J—C "broke up with" J.
The dispute itself is not the cause of the break.

SHORT POE
This question is hard.
The correct idiom is DISPUTE OVER,
not DISPUTE ABOUT.

Now we are down to A, B, and C.

(B) does not make much sense.
Camus broke with Sartre over bitterly disputing the nature of Stalinism.
-- ask which works better: disputing, or a dispute (GMAC often prefers noun forms to ING constructions)
-- in this case, "over" is in the wrong place. Dispute OVER, not "over a dispute."
-- is (B) as clear as (A) or (C)?
B vs. C may be hard to call, but B vs. A is not a hard call.
(A) is clearer.

Now, A or C?
As noted above, (C) does not tell us WHO was in a bitter dispute.

Answer A is best.

Having these replies is invaluable.
Many people will have used identical or similar thought processes
in both the correct eliminations and the incorrect ones.

I appreciate everyone who contributed!

dave13 has the best explanation (and the only correct answer)
kudos!