Re-order Paragraphs

1) 1971 war changed the political geography of the subcontinent
2) Despite the significance of the event. There has been no serious book about the conflict
3) Surrender at Dacca aims to fill this gap
4) It also profoundly altered the geo-strategic situation in South-East Asia
Answer: 1423
A. 1324 B. 3142 C. 2143 D. 1423

We can see that Option 1 is most likely the starting sentence. Now that we know that 1 is the starting sentence we can eliminate choice B and C as they start with 3 and 2 respectively and not with sentence 1.
This narrows down our possibilities to option A and option D.

Now we can see in option A 3 follows sentence 1 but the gap spoken of in sentence 3 has no correlation with political geography of the subcontinent spoken of in sentence 1 , so we can rule out Option A.
Therefore answer has to be option D, as we can also see it elaborates on the change mentioned in sentence 1.