A women was telling the heroic tale of her late husband to her grandchildren.
'When the First World War was about to end, your grandpa was awarded for his extreme bravery and heroism. While on the war, an enemy threw a grenade at their troupe. But before it could explode, your grandpa picked it up and threw it back on the enemy battalion. For this, he was awarded a sword with the engraving - 'Awarded for portrayal of extreme bravery and valor in the World War I'.'
Upon hearing this, one of the grand child stood up and said, 'You are fooling us with false story.'
The story was indeed fake. But how did he come to know that it was not true?