Identify the part which contains an error.
We are / in the final stage / of resolving the border dispute / among the two states.

Correct option is D

Option (d) contains an error.
Detailed explanation of error:
The phrase “among the two states” is incorrect because ‘among’ is used for more than two persons/things, whereas ‘between’ is used when referring to exactly two. Since the sentence talks about two states, the correct preposition should be ‘between’, not ‘among’.
Correct sentence:
We are in the final stage of resolving the border dispute between the two states.
Grammatical rule used:
· Between → used for two persons/things
· Among → used for more than two persons/things
Example:
· The agreement was signed between India and Nepal.
Information booster:
In competitive exams, preposition errors like between/among, since/for, in/at/on are frequently tested.