Final answer:
The United States entered World War II following a period of providing aid to Great Britain to help defend against German aggression, exemplified by the Lend-Lease Act. This was a prelude to the U.S. entering the conflict, which was prompted by Japan's attack on Pearl Harbor.
Step-by-step explanation:
The entrance of the United States into World War II was not an immediate decision but followed several preemptive actions and international policies. Predating the entry was American aid to Great Britain, a clear indicator of U.S. efforts to support allies against aggression without direct involvement in the conflict. The Lend-Lease Act, passed in March 1941, is a prime example of such aid, allowing the United States to provide military materiel to foreign nations deemed vital to the defense of the U.S. While President Franklin D. Roosevelt had been assisting Great Britain and navigating isolationist sentiment at home, it was ultimately Japan's attack on Pearl Harbor that propelled the U.S. into war.
Factual evidence suggests that option (3) American aid to help Great Britain defend itself against German aggression is the correct answer to the preceding actions to the U.S.'s entry into World War II.