The correct answer is option 5, i.e., C.

To DERIVE the last sentence of the correct arrangement, it is imperative to find out the FIRST six SENTENCES of the correct arrangement.
From the above solutions, we have been able to derive B as the first sentence, as per the question, 2 as the second sentence, E as the third sentence, D as the fourth sentence, 5 as the fifth sentence (given by the question) and A as the fifth sentence of the correct arrangement.
At this point, we are able to derive that the first six sentences of the correct arrangement are B2ED5A. 
The only sentence that we are left with is C, which logically MAKES the last sentence of the arrangement. Also, it talks about an actual meeting between the two countries on a concluding note.
Now, we have been able to derive that after B2ED5AC form the correct arrangement. On the basis of this, we can also state that C or option 5 makes the last sentence of the right arrangement.
Therefore, the correct arrangement is B2ED5AC. 
Hence, C or option 5 forms the right answer.