Explanation

The attack on Pearl Harbour (B) by Japan on December 7, 1941, directly led the United States to enter World War II, as it prompted a declaration of war against Japan and its allies. The Invasion of Poland (A) occurred in 1939 and involved European powers, not directly the US. The D-Day Invasion (C) happened in 1944, after the US was already in the war. “None of these” (D) is incorrect because B is the correct answer. Correct Answer: B. Attack on Pearl Harbour