Answer:
Option A.
Step-by-step explanation:
The United States, is the right answer.
The Peace Conference which formally put an end to the Russo-Japanese War in the year 1904-1905 is known as the Treaty of Portsmouth. It was approved on 5th September 1905, following the discussions lasting from 6th August to 30th August, in the United States. Theodore Roosevelt, the then U.S. President played a significant role in this negotiation and for his efforts he received the Nobel Peace Prize.