More than seventy years after the end of the Second World War, with which country has Japan still not concluded a formal peace treaty because of an unresolved territorial dispute?

Introduction / Context:
Although the Second World War ended in 1945, not all of the related diplomatic issues were fully resolved immediately. In some cases, territorial disputes and political tensions prevented countries from signing complete peace treaties. One well known example involves Japan and a neighbouring power, which still disagree over control of certain islands. This question asks you to identify that country.

Given Data / Assumptions:

• The conflict is the Second World War, which ended in 1945.
• The question refers to a peace treaty that has not been concluded even after many decades.
• The reason is an unresolved territorial dispute over islands.
• The options list India, Russia, China, and Canada.

Concept / Approach:
The unresolved peace treaty issue concerns Japan and Russia. At the end of World War Two, Soviet forces occupied several islands north of Japan, which Japan calls the Northern Territories and Russia calls part of the Kuril Islands. The two sides never fully agreed on their status. As a result, Japan and the Soviet Union, and later Russia, did not sign a formal peace treaty that settled all wartime issues, even though they have diplomatic relations. Japan and India, Japan and China, and Japan and Canada have treaties or at least do not have this specific long standing peace treaty gap from World War Two.

Step-by-Step Solution:
Step 1: Recall that the disputed islands lie between northern Japan and the Russian Far East.Step 2: Understand that both Japan and Russia claim some of these islands, and this dispute has blocked a final peace treaty.Step 3: Recognize that India, China, and Canada have different historical relationships with Japan and do not share this specific unresolved World War Two treaty issue.Step 4: Identify Russia as the modern successor state to the Soviet Union, which fought Japan in the closing days of World War Two.Step 5: Choose Russia as the country with which Japan has not concluded a formal peace treaty because of the island dispute.

Verification / Alternative check:
News and history sources often mention that Japan and Russia continue to negotiate over the Kuril Islands or Northern Territories and that this dispute has prevented a full peace treaty even decades after 1945. They also note occasional high level meetings between Japanese and Russian leaders to discuss the issue. In contrast, Japan signed a peace treaty with many other Allied countries in the early 1950s and does not have similar unresolved World War Two peace treaty questions with India, China, or Canada.

Why Other Options Are Wrong:
India and Japan have normal diplomatic relations and trade ties; there is no major unresolved World War Two peace treaty between them.
China and Japan have historical tensions and disputes, but they normalized relations in the 1970s and do not face the specific formal peace treaty gap described here in the same way as Japan and Russia.
Canada was part of the Allied side but signed peace treaties along with other Western countries long ago and does not have a territorial dispute with Japan blocking a treaty.

Common Pitfalls:
Some learners may choose China because they know that Japan and China have territorial disputes in the East China Sea and a history of conflict. Others may simply guess based on current news without recalling the specific World War Two context. To avoid this, pay attention to the clue about a peace treaty not concluded even after many decades due to island disputes in the far north, which is a well known feature of Japan Russia relations.

Final Answer:
Japan has still not concluded a formal World War Two peace treaty with Russia because of the unresolved territorial dispute over the Northern Territories or Kuril Islands.