The correct answer to the question "What event marked the beginning of the Cold War?" is:
c) The invasion of Poland by Nazi Germany
Explanation:
1) The invasion of Poland by Nazi Germany in September 1939 marked the beginning of World War II. This event is considered a significant trigger for the start of the Cold War between the Soviet Union and the Western powers.
2) After the defeat of Nazi Germany in World War II, tensions arose between the Soviet Union and the Western Allies due to ideological differences and conflicting interests.
3) The division of Germany into East and West after World War II further escalated these tensions, leading to the Cold War, a period of political hostility and military rivalry between the Soviet bloc and the Western bloc.
4) While the bombing of Pearl Harbor and the dropping of the atomic bomb on Hiroshima were significant events during World War II, they did not directly mark the beginning of the Cold War.
Therefore, the invasion of Poland by Nazi Germany is the event that marked the beginning of the Cold War due to the subsequent geopolitical developments and tensions that followed World War II.
