What was the diplomatic result of the invasion of Poland in World War II?

Correct answer: Britain and France declared war against Germany

Germany invaded Poland on 1 September 1939. Britain and France had security commitments to Poland, and when Germany did not withdraw, both countries declared war on Germany on 3 September. This diplomatic decision changed the Polish crisis into a wider European war and marked the beginning of World War II in Europe.

Option A is therefore correct. Germany did not enter the United Nations as a result of the invasion; the organisation was created later, in 1945. Poland certainly did not rule France, and Japan's actions in Asia were not a decision to leave Europe. The key point is that the invasion activated the commitments of Britain and France and caused them to enter the war against Germany.