Answer:
A
Explanation:
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Product of the Cold War it seems,
On 1949, US government received an official confirmation that the Soviet Union had developed  a Nuclear bomb.
To maintain the upper hand, President Truman approved the development of the hydrogen Bomb, an equivalent to 500 Atomic Bombs.
        
                    
             
        
        
        
Answer:
September 1, 1939 – September 2, 1945
Explanation:
Many Americans opposed the President. These “isolationists” believed that Americans should not be involved in a war fought in Europe. This attitude changed when the Japanese attacked Pearl Harbor.