Step 1 — Read all the parts:
A. in different regions of that federation
B. that was Yugoslavia
C. the fundamental cause has been the very large difference in the quality of life
D. although the dismemberment of the federation
E. is seen more as the result of an ethnic conflict
Step 2 — Identify the starting point:
Part (A) begins with "in different regions of that federation," which looks like it must follow a noun phrase. Part (B) "that was Yugoslavia" identifies the federation. Thus, (A) and (B) should come together at the start: "In different regions of that federation that was Yugoslavia..."
Step 3 — Connect the rest logically:
After establishing the subject, we need to bring in the clause about the cause: (D) "although the dismemberment of the federation" logically introduces the contrast. This is followed by (E) "is seen more as the result of an ethnic conflict."
Finally, (C) "the fundamental cause has been the very large difference in the quality of life" completes the idea.
Step 4 — Reconstruct the full sentence:
"In different regions of that federation that was Yugoslavia, although the dismemberment of the federation is seen more as the result of an ethnic conflict, the fundamental cause has been the very large difference in the quality of life."
Step 5 — Conclusion:
Thus, the correct order is ABDEC.
Final Answer:
The correct option is (D) : ABDEC.