Final answer:
The Axis powers declared war on the U.S., and the U.S. declared war on Germany, Italy, and Japan in 1941, following the Tripartite Pact and the attack on Pearl Harbor.
Step-by-step explanation:
Declaration of War Dates and Participants
The war declared by the Axis powers on the United States and the subsequent U.S. declaration of war on Germany, Italy, and Japan took place in 1941. Following the Japanese attack on Pearl Harbor on December 7, 1941, the United States declared war on Japan on December 8, 1941. In response, as per the Tripartite Pact, Germany and Italy then declared war on the United States on December 11, 1941.
The Impact of the Tripartite Pact
The Tripartite Pact, signed by Germany, Italy, and Japan in September of 1941, played a critical role in the sequence of events that brought the United States into World War II. This strategic alliance suggested that if one of the signatories was attacked by a country not already involved in the war, the others would declare war on that country. This pact essentially sealed the fate of the United States' entry into the war after the Pearl Harbor attack.
Therefore, the correct answer to the question is c) 1941.