The answer is C, the US successfully tested an atomic bomb.
Friedrich Wilhelm Rudolf GerhardAugust, Freiherr von Steuben, a Prussian military officer, arrives at General George Washington'sencampment at Valley Forge on this day in 1778 and commences training soldiers in close-order drill, instilling new confidence and discipline in the demoralized Continental Army.
Answer: December 25, 1991. It ceased to exist 12/31/91
Explanation: