The Amber Room belongs to the eight wonders of the world. It was given the name because almost several tons of amber were used to make it. First it was designed for the palace of FrederickI. Then Frederick William I, the next king of Prussia, sent it to Peter the Great as a gift of friendship from Prussian people. Later, CatherineII had the Amber Room moved to a palace outside St. Petersburg where she spent her summers and she told her artists to add more details to its design. Unfortunately, during the Second World War, the Nazi German was at war with Russia. In September 1941, the Nazis secretly stole the Amber Room and sent boxes of the Amber Room on a train for Konigsberg. After that what really happened to the Amber Room remains a mystery. The reason for the missing of the Amber Room is   _  .
the Second World War the disaster the time none of the above